what is it that cause so much back pain in the USA?

anecdotal evidence, but after a few years there I had weekly visits to chiropractic just to function. one week out of the country, anywhere else, and I am good as new again. back to the usa, back to chiropractic. I already tried to change everything I can think of. even doing more exercise in the us caused a nerve pitch that was hell.

why? why?