which of these do you think is most likely? I thought they were already using usa-based cloud infrastructure

All of these will be happening as well as hundreds of other moving pieces (domain name transfers, DNS changes, adjusting compute resources to maximise existing contracts with providers, migrating metrics systems impacting alerts and infra scaling etc etc etc). It's impossible to say from the outside which of these are causing issues.

> I thought they were already using usa-based cloud infrastructure

Unless they were already using the same provider on the same account with the same IAM policies as their new owner (they were not, obviously) this is irrelevant.