Why people who oppose illegal immigration say that we are invaded by them?

don't be silly, roaches invade your home; ants invade your garden. It means nothing more than an unwelcome incursion that one can only successfully meet with a countervailing force. Bugs don't have strategies; they swarm. No, the term isn't used primarily by white supremacist groups. Only people who think that people who walk into this country without being asked, or asking first, should be escorted out.