Too many.
As a child my Mom took us on three different cross-country trips.
Two were the West Coast where we spent Two Months in an RV (That's right, Mom, Stepdad, and my two siblings in ONE RV) going up and down the coast visiting various National Parks. It was basically a sight-seeing trip, we did nothing but visit tourist spots.
The other one was the South East where we went in the RV again to Tennessee and a couple surrounding states.
I'm also not mentioning the trips I've takek to Texas on a yearly basis, the New York trip, Florida trip and Canada trip.
Now that I think about it I've traveled A LOT in my life, at least around the US. The only time I've really ever traveled on a plane were regular trips to California, Florida and when we went to the UK and Scotland. I hate planes and prefer road trips (say what you want I'd rather be the one in control).
As far as National Parks...I have no idea I've been to so many. Of course naturally my Mom skipped over most of the famous one's like Yellowstone and the Grand Canyon. Although I remember the badlands, the giant crater in New Mexico, some big park in Utah, Mount St. Helens, Bryce Canyon, the Smokey Mountains off the top of my head.