Even for remote jobs being in a similar time zone is important to avoid slowing down communication.
Go check the “Who is hiring?” thread. About 90% of jobs at US companies that are remote, are “Remote (US)”.
This is much different from a few years ago.
I don’t know what happened, but my guess is that there are many more American software engineers looking for a job, so there is plenty to choose from within the US (which seems an easier hire in terms of bureaucracy and cultural similarity)
It used to be almost no remote jobs at all. With Covid a lot of the jobs that were US only became "Remote (US only)". And over time a lot more timezone restricted ones appeared.
ed: Had Claude put together a small analysis of it: https://bewelge.github.io/whoIsHiring/
So the share of US-only remote jobs seems to have been steadily increasing as long as remote jobs have been increasing.
I would say that the analysis is still underestimating the US-only jobs. It is common to not say it in the HN post, but when you check that actual job post page, you see it is US-only.