> except security is a bit worse (unless you have PreCheck and Global Entry, in which case it's actually quicker and easier than before).
Security is worse everywhere, even if you have PreCheck.
For starters, the rules for PreCheck are completely arbitrary and up to both the airport, terminal, and the whims of whoever is in charge that day. Even using the same checkpoint at the same terminal, sometimes you'll have to take your laptop out, sometimes you won't, sometimes you'll have to go through the scanner, sometimes you'll be able to use a metal detector, etc. Before 9/11, it was much more consistent (in large part because they didn't care about most of those things).
In addition, the inability to take arbitrary liquids (and more recently powders) is a huge inconvenience that wasn't in place before 2006 (and 2018).
> It's also been my experience that American airlines are pretty bad across the board. The European and Asian ones are typically much nicer, and even their regional/budget airlines have very nice accommodations and check-in experiences compared to United, etc.
This is a common perception, but having flown a lot within Europe and Asia, I disagree with this. One reason people perceive this is because they're used to comparing European airlines on international routes (where they are often, but not always, better), and because of the geography. Many of the popular US domestic flights are coast-to-coast, which results in a six hour flight. There's nowhere in the EU where you'll get a six-hour domestic flight - LIS to HEL is only 4.5 hours, and that's about as long as you'll get[0]. If you fly, say, AMS-WAW or AMS-BER, even on KLM, you'll get pretty minimal service on a narrow body with no in-flight entertainment or WiFi. And that's considered acceptable because it's a pretty short flight. But it's not exactly a step up from what you'd get on a comparable length in the US.
This isn't to excuse US airlines - as a frequent flyer, I'd really love better service on domestic flights. But it's an apples-to-oranges comparison: flights within the EU are shaped differently from flights within the US, and if you compare flights of similar lengths and similar levels of competition, the gap is pretty small.
As for the regional/budget airline difference... I don't know if I'd agree with that either. Is Spirit really worse than Ryan Air?
[0] You can stretch further by going as far as KEF, but at that point you're flying FI, and even though they've gotten a little better now that they have to compete on their international flight routes, I would not want to fly them for any long-haul flight if there's another option.