Dead right.
Do all exams and medical over here, then go out there expecting to be totally knackered for a number of weeks. That's how I got my IR. If I had even gone out for a beer or two each evening I would not have got it, and I had 500+ hours and a lot of instrument time then.
The PPL should be less intense but somehow one has to clock up the required hours.
If I was doing this "JAA PPL in the USA" stuff I would make sure I ended up with the FAA PPL logbook entries too and did the FAA checkride; then you have both the JAA PPL, and the FAA PPL which will be a standalone one and not dependent on anything but a Class 3 medical (which you can get out there, very cheap) and a BFR every 2 years, and the BFR can be combined in the same flight with a UK PPL checkout. This opens up the route to an IR. However, the FAA PPL requires additional revision over the JAA one, even though most of the JAA cr*p is missing from the syllabus.
Having invested the vast amount of hassle getting the visa and TSA, may as well make the best of it.