Almost anything is "possible", but this seems entirely implausible, based on extrapolation that goes at least an order of magnitude beyond anything supportable by evidence or careful argument. Can you name any other examples of this happening throughout history, in the US or anywhere else, where a completely self-isolated tiny minority group took power and displaced everyone through "out-procreating" them?

To be honest I really dislike this kind of vague speculative fearmongering when targeted at specific minority groups, which seems extremely dangerous. It historically blends right into overt bigotry and sectarian oppression.

The US has a long, proud tradition of all sorts of unusual sects and cults trying to do their own thing, often in somewhat closed communities, sometimes to the dismay of their neighbors, sometimes failing pretty badly, but usually without really breaking fair laws or causing serious mischief to anyone else (but also occasionally breaking a lot of laws and hurting people; the police should go after such cults). We all owe quite a few of the rights we take for granted to the hard struggle of some of these groups to make their own choices.

>Can you name any other examples of this happening throughout history, in the US or anywhere else, where a completely self-isolated tiny minority group took power and displaced everyone through "out-procreating" them?

Kiryas Joel NY, Lakewood NJ, certain parts of Brooklyn. They basically have their own government, and they have far less state government oversight due to politicians not wanting to go against them.

They drive around NYC with vehicles that look like cop cars, acting like cops, which would get most other groups charged with impersonating a government official. They elect themselves to the school board and vote to prioritize funding for their group’s children, and deprioritize funding for any other group’s children. Etc etc.

Not that they are the only group to have done it, but these are your easy to google examples.

> To be honest I really dislike this kind of vague speculative fearmongering when targeted at specific minority groups, which seems extremely dangerous. It historically blends right into overt bigotry and sectarian oppression.

Basically, I'm repeating the contention of sociologist Eric Kaufmann's book Shall the Religious Inherit the Earth–that in the long-run religious (ultra-)conservatives will dominate due to high birth and retention rates.

It isn't "fearmongering", because that assumes one is presenting a takeover by religious conservatives as negative. One might view it as positive. One might view it as neutral. I'm not presenting any value judgement of it here.

The contention isn't about any religious group in particular, it is about ultra-conservative religious groups in general. Ultra-Orthodox Jews happen to be the clearest example of the phenomenon, but there are other candidates – Old Order Amish, Latin Mass Roman Catholics, Salafist Muslims, etc.

Personally, I doubt ultra-Orthodox Jews will ever single-handedly takeover America, because in the scenario I am talking about, there will likely be other (non-Jewish) ultra-conservative religious groups, with which they'll share power. But I do think it plausible that in 2 or 3 centuries from now, North America will be a much more reliigious and much more conservative place than it is today. Not certain, of course, but plausible.