Looks like the standalone FAA PPL is the way to go. Sigh. Really look forward to all the TSA clearance paperwork and wait and ground exams and orals and...
But just as an aside. I've read a bit about the nutjob Maurice Kirk and his mad exploits flying around the world. Now, as I understand it, not only did he crash his G-reg Cub in the US, he bought a new one there, put it on the G-reg and flew on (the one he landed at Bush's ranch)! So it must be possible to get G-reg aircraft registered, signed off and maintained whilst abroad.