I was confused by this too. 5 GHz channels with 40/80 MHz width definitely work for me, without having to set a regulatory domain.
It appears that this problem is related to Intel's WiFi firmware automatic detection of the regulatory domain, which is LAR. This is done on the basis of nearby access points, although the specifics of how this works is beyond me.
The problem is that if this gets detected incorrectly, there's no way to override. What the users in this bug report found that attempting to set the regulatory domain manually resulted in two separate regulatory domains being defined, which still left the 5 GHz channels disabled on their devices.
A workaround for this firmware issue, previously, was to disable LAR, which would force the card to use the manually set regulatory domain. But this option was removed from the kernel due to it causing other problems.
So I don't think this is (exclusively) a non-US issue, it's an issue for people who live in a place where nearby access points will teach the WiFi driver the wrong regulatory domain ... however that works. It's probably less common for this to happen in the US, but not impossible.
Partially contrary to the title, I would expect this problem to affect a relatively small number of users.
Edit: I found a great blog post talking about the issue in more detail, although it's from the point of view of hosting an AP on the device. https://tildearrow.org/?p=post&month=7&year=2022&item=lar