In the last several years I have been to Death Valley, Yosemite, Zion (including Kolob area), Bryce, Capitol Reef, Grand Canyon, Cedar Breaks, Grand Staircase, Valley of Fire, Snow Canyon, Goblin Valley, Kodachrome Basin, Bodie, Mono Lake, Cathedral Gorge, Bristlecone Pine, Red Rocks, Coral Pink Sand Dunes, and places that should be protected but aren't (San Rafael Swell prominent among them). Most tourists from overseas are on the tour bus circuit, so unless you frequent the main overlooks, you won't encounter too many. We are usually up early for pre-sunrise shoots so rarely run into anyone except other photographers or people who like sunrises. But for sunset, the odds lengthen for crowd encounters, especially at iconic viewpoints as Bryce's Sunset Pt or Yosemite's Tunnel View.
Other foreign visitors, especially Europeans, love our Southwest because it is so unique as is our cowboy history. As mentioned above, most are respectful to our parks and open spaces. And quite a few speak better English than many Americans. Because they have longer vacations than we typically have at home, they will spend 2-3-4 weeks here, renting a car, van or RV. I think we take our national parks, state parks, open space for granted, as it IS our idea. We Westerners are probably more jaded than others as we have larger, more famous parks than other parts of the country.
As stated above, most foreign visitors are in awe of our country but people are people everywhere. A few must be completing a bucket list as they drive way over the speed limit (Yosemite is really bad on those hairpins), passing you to stop at the next overlook that you also stop at. I have talked to rangers who acknowledge the speed problem (kills bears, people, other wild life) but funds are tight and what can they do.
Statistics? AS stated not much out there for an objective tally but many come to our parks from all over. I read that the Europeans discovered our Southwest about 20 years ago and now the word is out. I encountered Czechs, Poles, Russians, East Indians, Chinese so not just the Western Europeans visit. Hopefully they will continue to come so those small towns along Utah's Hwy 12 won't dry up and blow away.