How many Canadians? In 2014 an estimated 52,513 Canadians sought care in the US - out of a population of 35.54 million. I could not find numbers of Britons coming to the US - they are far more likely to go to the EU. Estimates for Britons in 2014 range from 63,000 to 200,000 (the former is an official figure), in a population of 64.61 million.

How many Americans went abroad for medical care in 2014? 1.25 million.