Is the US printing a new 2 dollar bill commemorating national parks?

No they are not. Any of the national park $2 bills you see for sale are a standard bill printed at the Bureau of Engraving and Printing, U.S. Department of the Treasury. A non government business then takes these standard $2 bills, prints the extra color etc. onto the standard bill and refer to end product as a "privately enhanced" collectible. I doubt these bills will ever be worth much more than 2 bucks, as they are not an official US product.

They are currently being offered on TV, two for $10 plus S&H, but there is generally very little aftermarket demand for these items. They are interesting if you want to own one but they are definitely not an investment item.