You definitely don't have to go to the USA to get your FAA 61.75. I did the whole thing with a few phone calls and travelling no farther than farnborough in uk. You do have to the flight review and ground part to validate so you can use the certificate.
I have posted previously an easy step by step guide to do this without leaving the uk. I did the bfr (a very detailed 2 hours plus ) at my home airfield.
For me the only downside to the 61.75 was I made the mistake of moving house which means I need to repeat the process.
I would love to have enough time to go to USA and do some flying. However if time is at a premium as it was for me, you can easily do the whole thing here
It was actually the new York fsdo who so helpfully pointed out to me whilst they would be delighted to see me, why didn't I just do this without leaving london. They were very helpful.*