> Weekly church attendance in the U.S. is far higher than in Western Europe
Yes, but we were talking about western Europe, like Poland and Hungary.
> The U.S. isn't a "secular nation" either. The "Establishment Clause" prohibits Congress from establishing a national church, just like Article 137 of the Weimar Constitution in Germany
Yes, but we were talking about Poland and Hungary, not Germany. Poland and Hungary's constitutions establish national religious law. I would consider Germany to be secular, like the US, as opposed to Poland or Hungary, which are not.
> Justice Story made clear in 1830 that the constitution was not understood to prohibit non-preferential government support of religion
However, throughout the later 1800s, a majority of states (and nearly the nation as a whole) passed Blaine amendments, banning the use of public funds for private religious schools. Now this might have been driven in part by anti-catholic sentiment, but no, I don't think you can claim that the court adopting an interpretation that most states already had adopted was a "dramatic departure". Perhaps legally, but not in terms of popular support/understanding.
> particularly due to the Supreme Court taking various decisions on social issues away from the electorate, the laws in the U.S. with respect to churches, abortion, etc.
Right, and this is unambiguously a good thing. Laws shouldn't be based on religious ethics.
> And does that give us any insight into the current situation in the US?
Honestly, I don't see how it does. Trump's brand of populism isn't particularly religious. His appeal to the religious right wasn't much beyond "I'll appoint conservative judges". It's much more nationalist than religious (and I'll grant you that those two things are often intertwined, but that seems to be more because conservatives are often the ones stoking nationalist sentiment, and also they're usually more religious, I don't think religion necessitates nationalism).