Thanks. I'm presuming the hotel themselves won't know, as any bill is in local currency? I stay in the same hotel so don't want to cause any issues by somehow making it awkward for them.
Also, I'm guessing the vast majority of UK banks take a fee for converting dollars into sterling - so a couple of extra % cashback on the US site is wiped out by the bank conversion.

Basically - is it really worth it and actually any more profitable after fees?