The issue with parody is that you can't necessarily borrow one party's IP to parody another party.
You can do McDowell's to mock McDonald's, but using Mickey Mouse on your mouse pest control van would be a problem.
The safer element is that fair use (of which parody is a type) looks a lot to whether the use is (1) making money and (2) usurping a market the IP owner might enter.
Santa Clarita is arguably making money from tourism boosting, but they're not selling the posters. And it's unlikely Rockstar would be planning to use GTA on Santa Clarita posters.
Santa Clarita has a pretty decent case. Rockstar could send a cease and desist letter but it'd probably create bad press, and if anything this is advertising for them and the notoriety of their game.
(Ex IP Esq)