I'm not saying it's funny or polite, but when you realize that Democratic politicians are more of a foreign occupation than "our representatives," it's - not surprising that people say such things.
(And I do not mean to imply that Republican representatives are particularly representative, either.)
No, Democrats are not a foreign invasion, or anything like a foreign occupation. Democrat politicians represent a portion of America, and not a small one. Maybe not the political spectrum of the preference of the folks here, but still a portion of the American citizenry. Right or wrong, we have our current government because it is somewhat moderately accurate reflection of the population as a whole. Add in more dishonesty, corruption, hubris, etc of any large organization and the inherent evilness that seeps into any elected official, but still.
It's easy to forget that when you mostly talk to like minded folks, or are overly dismissive of other ideologies. When the Left does this, folks call it "echo chamber". Modern tech tends to reinforce that, by giving people access to other very like minded individuals.