And Hetzner works just fine for most small startups even if/when they have a US audience - the latency is perfectly manageable, though in those kind situations you will certainly want to expand into other regions later.

The main point, though, is that even when you scale, nothing stops you from using Hetzner for Europe, and e.g. OVH for US, and indeed filling in with things like AWS when there are needs you can't otherwise meet.

In reality very few startups gets to a scale where this starts to matter, and overoptimizing for it at the cost of infra spend at the start is a great way of running out of money - seen that happen way too many times.