What, exactly, would prevent this from happening in East Orange, New Jersy? Time to close down immigration from the Middle East was ten years ago. Exactly what benefit do native American citizens derive from unchecked third world immigration? Not nearly enough to make it worth this kind of disaster.
Ditto.
It could happen anywhere in the USA --- this massacre in Russia was a test run --- also Russia's government is still in chaos and doesn't have the ability to watch for this kind of thing as well as ours. I would guess something like this will happen in a country like Mexico for similar reasons. They could easily be thinking of a takeover of that country which would give them a big long muchly unguarded border to gain access to us.
Sadly this WILL happen in this country, without a doubt.