Au contraire. Cars Land is much more a perfect fit to California than any other Pixar addition to the park.
Bugs Land? Um, yeah, we have insects in California. But they are, lemme see now, yes, everywhere else in the world as well.
Monsters, Inc.? I don't recall anything about Monstropolis being the 3rd largest city in California - or, ahem, ANY city in California.
So ... Radiator Springs makes quite a big deal about it being located along Route 66 - which is quite a connection to California folklore. You're simply incorrect there, Moonie ... Cars Land is the most specifically California thing ever added via Pixar to DCA. Sorry.
Edited to inquire: Was it ever said in the film that Radiator Springs was not in the California section of Route 66? I mean, we might assume from the beautiful topography that it's in Arizona, but is it ever outright stated?