Minor nitpick: it was time to start worrying about Christian nationalism over twenty years ago. They’ve been trying to legitimize Christian nationalism since at least the founding of the “Moral Majority” when I was a boy. I’ve been trying to sound the alarm about Dominionism and Christian nationalism since the second Bush administration.
But if you’re late to the game, fine. The second best time to start worrying about Christian nationalism is now.
They’ve only worried about Sharia law taking over in the context that it was someone else’s Sharia law. It’s always about who holds power.