Scotland IS lovely, but you really can't beat flying in the States.
A Seaplane rating WOULD be fun. If you decide on this option, PM me and I'll suggest a good place.
My choice though would be to fly to Vegas, rent a plane and from there, you can do the Grand Canyon, then maybe fly out to San Diego, then up the West Coast.
If you plan on flying in the States and don't already have an FAA licence (the FAA will issue you a PPL based on your UK licence) - then you need to start sorting one out ASAP.