1. You don't need a Social Sec. #. And you would not get one. New rules: you would only get an ITIN (looks like a Soc. Sec. #) from IRS to file a US tax return for US income - and am not so sure that you want one, however, you may need already one.
2. You can open a bank account. Visit a bank during your next stay in USA. An area with lots of tourists - like Florida - is the best.
3. Tell the bank to fill out an IRS "W-8" form; then the bank does not have to withhold part of your interest income.

You may also consider a dollar (sub account) at your UK bank. Or an off-shore dollar account from Barclays Isle of Man branch!?!