I didn't have "One of the larger global nuclear powers elects the dumbest man alive as president" as a Great Filter in my paper back in college, but it increasingly feels like a distinct possibility.
The U.S. will never recover from this. Why? Because when foreign nations decide whether to do a deal with the U.S. they will do it with only a maxmimum of 4 year timeframes in mind. Because any deal you do with a sane administration could quite possibly be ended by the American people electing someone who is batshit insane, and who is backed by a bunch of cronies, sycophants and morons.
Six years is a better bet, due to some legislature terms and the fact that a president will be in office for eight years unless they do something really stupid.
But considering the counterparties can be countries like South Korea, Italy, the Philippines, Argentina, and Brazil, it's not like disruption isn't already baked in.
Imho going back before Reagan isn't really relevant. In the modern era we have Reagan (8), Bush I (4 because he raised taxes), Clinton (8), Bush II (8), Obama (8), Trump (4 because he botched covid), Biden (4). Biden would probably have been re-elected were it not for the cognitive decline, so he didn't exactly do anything wrong enough to be a single-term president.
Hungary isn't trying desperately to hold onto "single most powerful country in the world" status. The US being as relevant as Hungary is one of the most extreme scenarios of "The end of Pax Americana".
Well, when it happens to the level that it has under Trump, that country is in big trouble also. But noone (and I mean noone) has damaged a democratic nation as badly as Trump. There are a lot of contenders, but they all miss the mark by quite a bit.