I sadly believe you underestimate the docility of the American population, even the gunowners. And the government can berelied on , I think, to viciously side with the local Moslems/Arabs in such a brawl. Determined gun confiscation would likely result. The members of the bureaucracy and most of the bureaucracy are suicidally tunnelvisioned and will die before they let anyone have any excuse to label them unPC.
That I would like to see them try. Can't think of a good method for winning such a conflict. But if they were dumb enough to do that, this would be such a scenario.