Remote locations are where companies frack and spill oil and coal waste with impunity. People are also more likely to drink well water there (apparently 15% of Americans rely on it).

Coming from a rural place where water smelled like rotten eggs on a good day, I doubt the veracity of the claim.

With that 'logic', Russia is way cleaner - bigger, much more remote, much less population. Anyway we talk about country as a whole, and TBH I think there are cleaner countries but would love to see some proper stats.

Honestly, no. Many of the remote areas with water are contaminated from a century and a half of resource extraction -- often moreso than the cities because enforcement is lax when people don't live nearby. Most of the industrial revolution happened after the US had expanded to the Pacific.