People in Aus/NZ didn't mass turn in their guns. People in NY didn't register their guns when they were told to.
You need to understand the field for this is fertile. All we need is a sudden drop in standard of living or sudden hardship to accelerate this out of control. A growing amount of young men see no point in continuing to support this society. It would be easy to tack on all kinds of ideological positions onto a wide appeal issue like guns. You don't believe this will attract capital and aid from all kinds of groups that want the west gone?
This is ahistorical nonsense. I mean, don't get me wrong, I support everything that hurts and weakens the US. So, go for it!
But right-wingers are predicting a civil war and a day of the rope for many years now and nothing ever happens other than memes. The standard of living already IS dropping massively, even the live expectation for poor and working people is down, the younger generation of the US is already majority of non-white and nothing happens.
And who are these young men who will rise up anyway? For your prediction to happen you need young white men. Young white people only make up less than half of the US. Only half of those are men. Women and ethnics will hardly join your incel right-wing militia. Among those young white men not all are right-wingers anyway, not all believe in antisemitism.
And capital from outside groups: there's pretty much only Russia and China left that would be big enough to at least fund some groups here and there. And both Russia and China aren't doing that well right now due to sanctions and various other reasons, they might just as well implode themselves. And then there's the question if young white right-wing men even want to be associated with the Ruskies and the Chinaman. And they would have to pay them somehow. At the end of the day, they are mercenaries. US
soldiers mercenaries are murdering and getting murdered for a ruling class that doesn't have their best interests in mind for decades, there is no reason to believe that they would suddenly start shooting other soldiers if their commander in chief would declare war against China and Rusisa.
But as I said: go for it. Humanity's last hope might be a brutal civil war of Syrian proportions in the US. A civil war that tears this godforsaken country apart and then renders it weak enough to not longer dominate the rest of the world. And given the civil wars and "orange revolutions" the US has started all over the world (Syria and Iraq being the most recent and prominent examples) they would honestly deserve a taste of their own medicine.