Surely if one is working towards a commercial job, rather than flying privately, one needs to be strategic about which bits of paper one wants to collect.
Can one do a complete JAA CPL/IR or ATPL in the USA? I don't think so - European protectionism rules here.
If working towards a bizjet job then an FAA ATPL might be good (unless EASA succeeds is its currently published proposal to strip all European resident pilots of foreign license privileges while flying in Europe) but those jobs seem hard to get for a novice.
One can do a JAA PPL in the USA - half a dozen schools in Florida and one in California. Those hours will count back in the UK.