iPhones bought outside the US also have mid-band accessibility. I got my 15 PM in the UK (and also got Verizon to whitelist it got esim use), and can connect to everything but the genuine mmwave (n258-261) no problem.
Yes, aside from mmWave, 5G bands are fairly standardised worldwide. Generally speaking, a 5G phone purchased in one country will work fine on 5G networks in any other country.