Wi Fi availability at RV Campgrounds

All I know is Verizon is the carrier of choice for cell and data plans when traveling.We were in most of the places you mentioned over past two months and while Verizon customers were able to use their smartphones and iPads we struggled to get service of any kind with ATT. It's also been our experience that although most private RV parks offer wifi it's often in name only. The service is usually weakest in the evening when everyone has returned from sightseeing -so it's tough to get connection.
Have a great time on your 2015 trip. America is a beautiful country and RVers,for the most part, are the nicest,friendliest people on earth!

From what I have seen I would assume (although there may be some exceptions):
1) most national, state and provincial parks- No
2) most KOA and many other private parks- Yes (but often slow in the evening)

The other option is many restaurant chains have WIFI in nearly every store in both US and Canada like McDonalds and Starbucks

About the only place you may have to pay these days is hotels.