I agree that immigration is probably playing a role, perhaps even a significant one, in these numbers, but at the same time this is also expected even without immigration. Religious families are having more children which means that, over time, there would be an inflection such that a generation starts becoming significantly more religious than the one prior - even if it's 100% because the children of that generation were born to religious families. Bringing over large numbers of religious immigrants is just speed running this endgame.

Yes perhaps I should not have focused on immigrants when the overall question I want to ask is if this effect is driven by religious subgroups/subcultures which include both immigrants from religious countries as well as people from religious communities within the US.

My hypothesis is that we’re not seeing much of a “return to religious observance” from children of parents with low/no religiosity and that nearly all of the resurgence is driven by the aforementioned religious subgroups.