I was watching a video from two years ago about different social norms and this showed up. Found someone questioning the same eight years ago on reddit (when it seemed less normalized). It feels so weird not being aware of this shift, even as a foreigner.
Huh, I didn’t even know this as someone born and raised in the US. I do say “no problem” or “no worries” a lot more than “you’re welcome” these days, but I do tend to use the latter in more formal situations. I do think an “mmhmm” might strike me as cold or condescending. Then again, I’ve been out of the country for the better part of a decade now.