RE: criminal record going to usa
It depends on just how bad you've been...My cousin went to Florida for Xmas last year, got to O'Hare to change planes, and go through immigration. They scanned his passport, then allowed him to wave bye to his missus and kids who continued their holiday before they sent him packing on the first flight back to the UK. He has been a bit of a bad boy in the past..drugs, football fighting and theft issues...Not surprising they didnt let him in at all really, shame it wasn't Australia he was visiting, a record would have helped there!
On the other hand, I know of someone else who has been frequently, nevert mentioned his GBH conviction, and never had any trouble!