It's not just about chronic malignant threats like those countries; it's also about acute threats. Take as an example, if you were Ukrainian, you had about 2 months of runway during which there was ample evidence Russia was going to invade Ukraine and the country would likely be flattened. And yet, when Russia did invade Ukraine, there were throngs of people trying to escape. I'm not talking about people who are disabled or immobile, I'm talking about middle class people who simply thought they had more time and didn't want to disrupt their life for nothing. See also Afghans in Kabul, who thought either the Taliban wouldn't win or they'd have several more months to get their lives in order.
This is also a popular trope in fiction. In the recent Handmaid's Tale series, there are several episodes devoted to life immediately before the fall, and what you see is a lot of evidence stuff is going to hit a crisis point, and a lot of people insisting that it hasn't quite yet.
Obviously the threshold to act has to be fairly high -- and I'm not saying America is Kabul or Kyiv or Gilead -- but I think there's nothing wrong with listening to the part of your brain that says "wow, it feels like the shit is imminently going to hit the fan". Because if you wait until it actually does, you'll have significantly less capacity to act.
There are also options beyond leaving the country. Some places are physically safer and physically more isolated from threat than others. For example, in the event that there is a rapid institutional collapse in the United States, it seems likely that Hawai'i would be among the places most likely to endure a little while extra or to most easily facilitate leaving the country. Areas near unguarded border crossings on the northern border also have an appeal in that regard. I think the right degree of seriousness with which to take something like this is not so much "I should move to Hawai'i tomorrow in case there's a civil war" and more "If I can work remotely in Hawai'i or if a job opens up, I might gain some degree of personal safety/sovereignty by moving there."
Personal context: I am a non-American. I spent most of the 2010s living in the U.S., and I emigrated to another country in early 2021. The pull factor to emigrate was a job opportunity abroad that was great and that my wife agreed would be a fun way to spend a few years, but the push factor to emigrate was significant uncertainty about the institutional stability of the U.S. We were setting up our paperwork just as the Capitol Insurrection happened.