The USA has a huge military budget because:
 it values its freedom and independence
 it values its allies and trade routes
 it costs the USA a lot more to get any measure of military might since it does not have a conscripted military and its materiel is not made by government suppliers.
The USA has a huge military budget because:
 it has whipped it's population, and that of a significant portion of the worlds population, into a frenzy of fear and paranoia, by maintaining a permanent war status since the end of WWII. Whether hot or cold, the USA has waged war against non-enemies, aggressively supporting brutal dictatorships around, killing millions in defence of "freedom and democracy" around the world. The USA as "protector" of the "free world" has been holding the human species hostage to the possibility of imminent extinction via nuclear weapons for nearly 70 years now. This in the name of valuing its freedom and independence.
 it has decided that the best social control mechanism for social pacification is to provide the lowest possible cost for goods and promoted consumerism as ersatz status symbols for a largely disenfranchised permanent underclass. In order to secure such cheap access to goods, the USA must dominate all world trade and be able to dictate prices for resources, resource extraction, production and distribution. This in the name of valuing its allies and trade routes.
 it spends a lot less money for the size of our military than any other country would for a similarly sized and scaled military because 18 year-old's with no prospects always form a cheap labor pool( "sold" as in soldier, comes from Roman Latin, daily wage-worker), particularly if one can convince them that they are serving their country men in the name of noble goals and values like "freedom and democracy". And because military production in the USA has always been "dual-purpose", a civilian feel-good, while producing weapons of mass destruction.
The USA has co-opted a tremendously large section of it's so-called private market for dual-purpose: production of disposable goods, while supplying the worlds largest military with an endless production line of "goods", of which no good can ever come. Most major manufacturing firms in the USA would not be economically viable if it were not for this arrangement. Boeing could never make it solely producing commercial air-liners, the market for such is not large enough, but if the Pentagon needs x number of fighter jets, missiles and rockets every year, which must be constantly restocked, due to usage in wars or due to degradation from not ever being used, they can show a profit for their civilian production lines. The same is, and has always been, true for GM, Ford, GE, etc.
The USA has not, historically, HAD a "health service" because we traditionally left health to the people themselves, the private sectore, and communities and states (The US Constitution says nothing about healthcare, and it explicitly says that anything it does not assign to the federal government belongs to the people and to the states)
The USA has not, historically, HAD a health service, because immiseration is a constitutive part of maintaining an exploitable permanent underclass. During the first 250 years of American history, surplus value, ie. profit, was made primarily by either a) stealing the indigenous peoples lands or b) exploiting "free labor", ie. slavery. Following the civil war profit has largely been made by exploiting those born into inter-generational poverty, both here and around the world. The majority of Europeans who immigrated to the USA during the first 150 years of colonization were debt-prisoners, ie. the then european permanent underclass. The USA has proudly cultivated cultural identities for the permanent underclass, going back almost 350 years, nowadays we call them "rednecks", the "n-word", and "mehicans".
The constitution, written for the most part by by the 18th century 1%, actually went to lengths to prevent the existence of a standing army. The USA has been violating it's own constitution every day for nearly 70 years now by maintaining the largest scale military ever seen in world history in direct opposition to our founders intents. With a media hell-bent on scaring the bejesus out of everyone 24/7, covert intelligence services, dedicated primarily to propagating domestic propaganda(be scared, be very scared), and brutal police forces, who routinely terrorize, denigrate and humiliate our permanent underclass, we have held our population in line through domestic terror, knee-jerk reactionary patriotism, dog-whistle ethnic discrimination, and cultural envy as a function of permanently denying the permanent underclass of the USA access to the "freedoms" and "democracy", which supposedly are those things that make America all so great.
The reason I hate ads is because it's a legitimized way of abuse, of hurting other people. I'm gonna be a father at some point, and I dread the day I have to explain to my kid that modern civilization is in this weird state, where it's "friendly" in the sense that you don't generally have to fear strangers, but it's also overrun by malicious actors trying to suck your money and happiness dry. Our civilization pays lip service to being cooperative, yet so much of it is still adversarial.
But when they plunder from these miners, these children, my fellow citizens, countrymen, thrown out on the highways and mother insulted — do you think that they will be good citizens when they grow up? I don't. The revenge and resentment will be buried there if they grow into manhood, it will develop, they will kill, they will murder to get even with those who robbed them. I want you to stop that. I don't want it to go on. Your Governor may, but I don't. I want the children to have the best of influence, I want the children to have good schooling, I want women to know nothing but what is good, I want to leave to this nation a nobler manhood and greater womanhood. Can I do it? No, I can't, boys, with the administration you have got, I can't do it.
I can do it if you men and women will stand together, find out the seat of the disease and pull it up by the roots.
Take possession of that state house, that ground is yours. (Someone interrupted, and the speaker said "Shut your mouth.")
You built that state house, didn't you? You pay the public officials, don't you? You paid for that ground, didn't you? (Cries of: "Yes," "yes.")
Then, who does it belong to? Then why did the militia chase you off? You have been hypnotized. The trouble has been that they wanted the slave system to continue. They have had a glass for you and your wives and children to look into. They have you hypnotized.
We've changed. And we've become contemptuous of the idea that we're all in this together. This is about sharing. And about, you know... when you say sharing, there is a percentage of the population, and it's the moneyed percent of our population, that hears "socialism" or "communism" or any of the other -isms they wanna put on it, but ultimately, we are all a part of the same society, and it's either gonna be a mediocre society that, you know, abuses people, or it's not.
We have much studied and much perfected the great civilised invention of the division of labour; only we give it a false name. Truly speaking it is not the labour that is divided; but the men: – Divided into mere segments of men – broken into small fragments and crumbs of life; so that all the little piece of intelligence that is left in a man is not enough to make a pin.
Only in right understanding on the part of all classes of what kinds of labor are good for men, raising them and making them happy, by a determined sacrifice of such convenience, or beauty, or cheapness as is to be got only by the degradation of the workman; and by equally determined demand for the products and results of healthy and ennobling labour can this evil be met.
I can have no other notion of all the other governments that I see or know, than that they are a conspiracy of the rich, who, on pretence of managing the public, only pursue their private ends, and devise all the ways and arts they can find out; first, that they may, without danger, preserve all that they have so ill-acquired, and then, that they may engage the poor to toil and labour for them at as low rates as possible, and oppress them as much as they please; and if they can but prevail to get these contrivances established by the show of public authority, which is considered as the representative of the whole people, then they are accounted laws.
They [governments and corporations] take whatever is available, and in no time it is being used against us, the population. Governments are not representative. They have their own power, serving segments of the population that are dominant and rich.