OK, but I think currency is important in VMC too.
So, a year or more after you got your PPL, it doesn't matter where you got it. What matters is how many hours you clock up and doing what where.
If you save £3000 doing a JAA (or FAA) PPL in the USA and then spend the extra £3000 flying around the UK (about 30hrs in a rented spamcan) that's a lot of flying! It's about 18 months' flying, based on what I believe is a UK PPL's average annual time. Most people who get a PPL chuck in flying for good even before reaching 30 hours.
That said, going to the USA isn't for everybody. I could have never done a PPL out there - could not get 4-6 weeks off work, and it certainly won't be a holiday!