That's art, why can't it be the case? At some level it is the case.
Remember the, ho-hum, was it the... err, the Texas Chainsaw Massacre, the remake from a couple years back?
With all that US flag-waving, the mutants looking like inbred Mexicans on the loose, the protagonists a Johnny Average American family in their pickup and trailer and, super-camp, scene where the uber-mutant is killed with an American flag driven into its body? It just screamed "symbolic of the Latino immigration" to me, the whole movie, start to finish!
Symbolic undertones can perfectly co-exist alongside normal content, it's just another layer of the movie. Not everyone has to see it, not everyone has to agree with it, but it's potentially there for some folks.