I don’t believe it would be legal in CA for a car manufacturer to offer a warranty that is voided by something like temporarily removing a part.

You can modify your car anyway you want and it won’t void the warranty for unaffected parts, but the bumper warranty would be void and that’s like $2000 from the quote a colleague got from Tesla for a replacement bumper and paint.

The Magnusson-Moss act prevents arbitrary voiding of warranties.