When people from a particular country, to the tune of millions every year, knowling break our Federal Immigration Laws (among the other laws such as working illegally, driving illegally, driving without insurance, and committing various other crimes) and refuse to leave, what would your definition of that be if not an invasion.
I'm open to a redefinition if it make sense.
It's obviously not an invasion in the military sense of the word and a military response is not appropriate.