As mentioned, dogging, at least in the conventional sense, is pretty rare in the U.S.
Depending on where you live, there may be certain well-known spots for engaging in activity similar to dogging. Certain parks, rest areas, various outdoor venues, parking garages, and some establishments (adult bookstores, theaters, bars/strip joints) also have some of this action going on.
In Europe, there are forums and web resources that aggregate dogging locations, interests, etc., not so much in the U.S.
When Craig's List personals were still a thing, we tried a few times to organize dogging events, without much success. Pretty much our experience with risky public sex has been in locations where this is known to be a thing, and tolerated (i.e. no law enforcement interference).