I have been a user of galaxy phones for many years. I am shortly visiting the USA if I found a Samsung mobile there would it work fully without problems in the UK?
It would likely be locked to the USA. Yes, you could get it network unlocked so you could insert a different SIM, but you would unlikely receive any OTA firmware / security updates while out of the USA. I'd speak to the retailer for a more informed answer.
Some features may be specific for USA, and also can impact OTA updates.
But for calls texts etc then I don't think they'd be any issue as long as you have roaming on and don't have any restrictions on your sim plan and the phone supports your network IE not locked to a network provider.
Also, keep in mind that if you buy from USA your warranty will be for that region and UK support will be limited.
I can 100% confirm that you shouldn't, I know from past experience that Samsung pay won't work in the UK and you won't get 5g. The USA have different bands to us and it will be region locked, I hope this helps.
@TechZilla and others are correct, there would be major issues. A bit about thew different bands in Europe and US here .
"Europe has prioritised the 700 MHz band for wide area 5G and a growing number of countries globally are supporting the 600 MHz band1 (including the US which already uses it for 5G)"
