In the strictest sense of the word, I don't think there's a lot of it in the US. Not a lot of secluded foresty areas. Or at least not around me. But there are some spots you can hang out where you may run into an open couple or single.
I love the idea, either just watching or being watched has always been hot to me. Finding a random couple fucking in a car or park would be hot, just need to know the rules, many don't want someone to touch.