Well done. Yes, we in the US have been blessed, by our government setting aside some of Earth's finest examples of Mother Nature, for all to appreciate and enjoy. What other parks have you visited?
In 3 months time we visited 28 parks, and after visiting South America we crossed the ocean via Hawaii and visited 2 parks there as well. (so 30 total).
In 2012 (I believe), When I didn't had my driver licence yet, I did a West-USA Bus tour. we visited a few parks (I think 4 or 5), and apart from Death Valley, we visited those again (because a bus tour just doesn't give you enough time...).
So I guess my counter is at 31 one, Every park being beautifully and unique in its own way, just love it !
Al tough there are a few parks, that will need re-visiting, because it was winter and we missed out on stuff.
If you want to know all the parks, you can see the travel map of our world trip
here. Just zoom into the USA.