Disclaimer, I'm absolutely no expert.IMO is a combination of events. I think Covid stopping all flights for so long caused some permanent loss of institutional system knowledge, and we've never recovered from it since.
On top of that, the US has been having more and more shutdowns - and regardless of whether you like him or not, Trump's been responsible for some of the longest ones.
The impact of extra mental stress on people who're already in one of the most stressful jobs in the world cannot be good in any way I can think of.
I think the fact that we're not seeing so many issues in Germany or Singapore or Dubai makes me suspect that this is a bit more US specific than global. Some issues (eg Covid) are common, but an alert pilots can overcome eg a mistaken ATC. But the more things/conditions that go wrong, the likelier it is that the Swiss cheesehole misses and causes an error.
Richard Cook's How Complex Systems Fail is an interesting read if you're curious for more.