Freight or passenger, you will never fly a G reg aircraft commercially without a JAA license.

If you wish to fly for an American airline you will need a Green Card and a hell of a lot of luck.

Your best bet would be to try and get a job flying a European based N reg bizjet. The only problem with this is that there are literally hundreds of British FAA ATPL holders after these jobs and there aren’t many of them. Many of these are also unpaid positions.