The FAA PPL is accepted by the UK CAA for a G-reg plane, for worldwide VFR flight. This acceptance is automatic.
I don't know of another European country that does that. Others do various forms of validation but with various restrictions - largely to protect their domestic flight training business.
Flight training is NOT a holiday however. It is hard work. If you go to the USA for a holiday, hoping to pick up a PPL, forget it.
You also need to get the writtens and the medical out of the way before you go out there - unless you are going for quite a number of weeks.
I've sent you a PM.