If I were you, I'd take a look at some of the big UK banks that have offices in the US - HSBC, Barclays (at least in NYC).

I'd also take a look at the US professional associations for financial advisors and financial planners - something like the Certified Financial Planners here: Certified Financial Planner Board of Standards Inc. or the Financial Planning Association Welcome to the Financial Planning Association They may have some form of reciprocity with your UK qualification and they certainly can help advise you on training and examinations, as well as opportunities for working with expats.
Cheers,
Bev