It seems to me that barring Flint Michigan, which was a well known problem, the overwhelming majority of Americans are not being poisoned or sickened by their water supplies, which campgrounds and RV parks share.
So If you don't feel it necessary to have an inline filter at your house then why have one on the road? It seems odd to me to worry about the drinking water where people are living and carrying on their lives and drinking the water with no problems.
America does have some of the worlds cleanest water and highest standards. Trust me Iv'e lived in Egypt and SE Asia and know dirty water systems.
We worry way too much about stuff like this. And that is a function of our over-obsessive concern with all things bacterial. Most of which are actually either good for us or at least not harmful.
How DID I EVER live to be this age without sani-wipes to clean the grocery-cart handle and RV water filters?