I've followed US politics closely since the Obama era (though taking a step back to preserve my sanity these days) and if I am being blatantly honest I just don't see it happening.
A lot of US Americans seem to think Trump is the aberration rather than a moment that has been building for decades. You don't have a functioning democracy, but that's also not a recent thing. The Democrats completely fail to meet the moment (other than the DSA aligned politicians, but establishment dems are working hard against them). I hear so many Americans still proclaiming they're the best country in the world even though you never was and certainly aren't now. You wrote navel-gazing a few comments back - it's a very big problem.
And another side of the problem is that much of the world fails to treat the US as it deserves to be treated currently.
I can go on and on.
I think the most realistic scenario is the fall of an empire but no idea what comes after that. The land mass is still there and so are the people.
My best plan is to help the US build the wall on the southern border and build one to the north as well. Not to keep people out but to keep people in. Then ship all the good people to Europe while we ship all our bad ones to the US.