Hi Gordon
I'm in Oz and receive both the UK pension and a UK company pension. I was told that I had to pay UK income tax on them.
After a bit of research I found that the UK has a reciprocal tax arrangement with Australia whereby if you pay tax in Australia you don't then have to pay again to the UK.
I had to get a form from the UK tax office send it to the Oz tax people to certify that I paid tax in Oz and then sent it to the UK.
The idea is that people aren't having to pay double tax on pensions.
UK may have a similar arrangement with USA.
Check on the UK tax website.
Allan