Religious Jews vote Republican. Having Jewish ancestry doesn’t make you a practicing Jew, any more than having Christian ancestry makes you a practicing Christian.
Throughout the history of the Jewish people, there has always been a battle between the Jews who are faithful to the Jewish religion, and the assimilationed Jews. That’s what the story of Hanukkah was all about. It’s the religious Jews who keep the Jewish religion alive, and the assimilated Jews are like leaves falling off of a tree. The Jewish people are self-sustaining, because enough Jews pass on their beliefs to their children.
The more important question is will Christianity survive now that all the cultural institutions of the West that used to promote it now denigrate it?
I’m aware of the divide.
But these days it isn’t that one bunch is religious and the other isn’t but that both follow a religion, for the Left is a religion too, one that finds its mirror in Islam ... except where Mohammad’s disciples went out waging war ASAP because Allah’s kingdom is only in this world the Left is out to fix the world for much the same cause.
As for the true faithful, there is always a remnant. Christianity spread to the farthest reaches without the institutions you speak of ... and in a very real sinse those have made it easier for the unconverted to warm pews for the price of “not being” a Christian (or appearing to as men judge things) has sometimes been higher than being an actual believer.
Back in the day Christ told those who demanded a sign from Him that no sign would be given them but the sign of Jonah.
Now, were He openly walking among us, He might say that an evil generation will be given no sign but the sign of Romans 1:18-32.
Which we are being given, BTW.
Recall that Christ wondered if He would find faith when He returned for context.
And as I said, there’s always a remnant.