Do I believe the US is inevitably collapsing, like the Roman empire during its decline? No. But fixing everything from health care and significant income inequality, to the justice system and police force, to its crumbling infrastructure, to the damaged foreign relations, will take time and political effort, not to mention large amounts of money, which is a problem given the US' towering debt, which is apparently expected to become unmanagable by 2050. And that's before I even get into the dumbing-down and polarisation of American society, and the drift into a post-fact world where rational, unifying public discourse is all but impossible in the first place.
Honestly, if the trumpkins want to destroy their country this badly, and the opponents are so horrible, they should just let the blue states secede and leave the red states to rot. I'm thinking all the west coast states. Sacramento or San Fransisco could become the capital of the Blue States of America. Or maybe Seattle. I like Seattle.