"The rhyme of "California" with "warn ya" was probably funny once..."

Funny or not, it's a perfectly matching rhyme, not in any way strained.

Not that "accuracy" in rhymes is ever the determining factor in this kind of thing. In fact, the more "accurate" the rhyme, the greater the sense of bathos when it becomes clear that the verse has been pulled out of shape to achieve it. (Though of course that can be perfectly acceptable when a humorous effect is intended.)