The United States National Parks may all be closed right now due to the government shutdown, but you can always visit them in Google Earth!
The best place to start is the official “US National Parks” layer. You can find it under [More] –> [Parks/Recreation Areas] –> [US National Parks], as seen in the screenshot below.
Even better, you can explore many of these parks in Street View. You can check Hawaii Volcanoes National Park, various National Parks in California, and others around the country. Here is a view from Glacier Point in Yosemite National Park:
While some other online resources are unavailable during the shutdown, such as a great Google Earth KML of our local Kennesaw Mountain National Battlefield Park that was hosted by them (and is now temporarily disabled), there is still a wealth of imagery to explore.
If you know of other great National Park resources for Google Earth, please share them in the comments below.