How does America end?
America will not last forever, and I'm honestly worried about it surviving the next half-decade. The current administration is just the latest round of rot that has eaten away at America's core. The rot is the religious-level fascination with hyper-capitalism that is so common among the ruling class. For decades now, capitalism has eaten away at core institutions. Everything that used to be a unifying experience among Americans is now stratified by class. Public institutions that used to be accessible to all are now restricted to those with money.
The Institutions
The difference in life outcomes between various universities is enough to illustrate this contrast. The debate around college admissions seems to consistently return to affirmative action, but the word "legacy" escapes most scrutiny. Legacy, the method by which the rich ensure that their progeny will retain the wealth and elite status of their parents. It doesn't matter how smart the kid is, legacy insures that their resume will carry the name of a sacred educational institution. Education codifies American aristocracy.
Look at the press, where capitalistic forces have prioritized engagement over truth. Every news organization has optimized itself for its chosen market, tailoring its messages and its facts for maximum consumption. News has transitioned from information to entertainment.
The Christian church has, in the past, acted as a stabilizing, unifying force for the American public. But, in the past half century, the church has fragmented American society in almost every way possible. Between accepting capitalism as core ideology and choosing reactionary social politics at every turn, the church has lost and alienated increasing numbers of young people in each generation.
And then we have the capstone, the federal system. The Executive, Legislative and the Judicial. At this point in time, only the Judicial branch is functional, and the supreme court is on the verge of getting a new member who openly fawns over executive power.
So, what do we have left? What remaining threads do we share? Well, government services are pretty much all that's left. Medicare, Medicaid, the Post Office, Social Security are the only things that unify the American experience. With the exception of the Post Office, these cost a lot of money to maintain. These services are also all one prolonged government shutdown away from non-existence.
So, what happens when the checks stop arriving? Well, here we get to the "fun" part.
The States
The good thing about this country is that each state is basically its own country. Each state has its own three branches of government, so each state can become reasonably independent the moment the federal government ceases to exist. Each state can manage its own economy and its own laws, so except in cases that depend on government money (I'm so sorry, Florida), the states will be just fine. Built-up states can easily replace federal government services with local versions by raising taxes. Massachusetts will be just fine.
States with more resources can trade with states with less. Each state would have to determine its own currency, and there would be an exchange rate. Free of interfering factors, life should continue fairly normally.
The lack of any physical borders between states makes enforcement of traditional statecraft like immigration and trade controls laughable. Unless certain states truly go off the rails, there won't be much point in building border controls.
A good number of states may seriously consider annexation by Canada. Maine, for example, shares a lot of language and economic ties with Canada, and would be a likely candidate. The northern plains states may find common cause with their Canadian cousins and do the same. If it goes well, Canada could scoop up quite a few US states.
The Corporations
Corporations will remain powerful, and now federal regulations carry no weight. It will be up to each state government to pass laws constraining corporate power, but these laws will not cross state lines, so compliance gets a LOT more complicated.
The financial sector will probably crash, but it will be back with a vengeance. Assets are still valuable, and state judicial systems are still functioning. New York will have to figure out what role it wants to play, and it has a real chance of reforming a new federal government through its huge influence over markets.
The power vacuum will probably leave corporations with a lot more power in states that don't have a large public sector. They will be in a great position to bully state governments for exceptions or privileges.
In some states, key industries may be nationalized. I would imagine in agriculture-heavy states, a multi-national corporation running your entire economic output could seem very threatening. States would have to act fast before corporations could hire private security to prevent such a takeover.
The Military
The biggest single recipient of federal checks would be the US Military. Our military is goddamn expensive. Not only in terms of personnel, but also in terms of maintenance, fuel and ordinance. So, if the federal government collapsed, what would happen to all that stuff? Well, the first thing you would have is a bunch of soldiers who aren't getting paid. The vast majority that are supporting families with their salaries would have a strong incentive to go AWOL and seek other employment after a couple months with no pay. The rest could theoretically survive off of rations for a long time, but it's going to be a game of diminishing resources until the states pick up the tab, if at all. The fleets would probably return home, and foreign bases would quickly diminish. It is my optimistic opinion that most soldiers who choose to remain would choose protecting military assets as their primary objective. State governments SHOULD step up and provide resources to those who choose to stay.
But here's the thing about US military equipment. It lives on money. If you take away capital, it breaks down, and it doesn't get fixed. Russian hardware is notorious for repair-ability and reliability. You can take a Russian tank that's been sitting in a field for 20 years and get the engine started with a few hours of work. American equipment? Not so much. We build great stuff, don't get me wrong, but we put a gas turbine in a tank. If you don't know, a gas turbine is basically a self-contained jet engine. It requires expert maintenance and flawless replacement parts. A lot of US military equipment is built to similar specifications. To illustrate, we sold a bunch of F-14s to Iran in the '70s, and they literally can't fly them without replacement parts that only America can manufacture, so they have been sitting on the ground ever since they arrived.
So, some states that host military bases will find money in their budget to keep the stuff secure, but for the most part it will sit. In 10+ years, it won't even be useable. The various national guards will continue, with a tiny budget, but it would take a LOT of unrest to cause inter-state conflict.
The People
A lot of people depend on the federal government for survival, and a lot of those people live in states that can't afford to replace federal government services at a state level. The ones that live in well-off states can probably expect a degree of replacement services from state governments once they figure their shit out.
There will be a lot of federal employees out of the job. If states act fast enough, local administration can be incorporated into the local government.
Florida. It's sinking into the sea, AND now it has a very angry retired population with no income. Some of them will have guns. It won't be pretty.
The Future
Now, the question is how do 50 independent countries across a large continent play nice with each other? As long as economies stay good, probably for a long time. Some states might merge, split, or join confederations. I don't think it will devolve into a Mad Max-style wasteland, except for Florida, but that's going to be more like Waterworld than Mad Max.