I think the answer here is that religion was much more fundamental to American identities in 1776 than it is today. In US history and still today in other count

I think the answer here is that religion was much more fundamental to American identities in 1776 than it is today. In US history and still today in other countries there are lots of examples of people being violently persecuted for believing in a certain religion, much fewer for holding a political opinion. You could make an argument that in the US people of different religions get along better than they used to and as a result religion no longer requires the Constitutional protections it currently enjoys. I would respond that as a society we probably have bigger fish to fry.