"They have to define themselves in opposition to something.
And the last embers of the late 1800s Know-Nothing "These Damn Catholic immigrants are going to take over the country and hand it over to the Pope" paranoia have been surprisingly difficult to extinguish."
Well, yes. The Reformation had its roots in real problems with the Catholicism of its day. Catholicism, like all things, has changed since then. Yet some people still think you can buy indulgences in the public square, I suppose.
The fracturing of Christianity since the Reformation is fascinating to study. Most often, the fracturing has occured over extremely small doctrinal differences. It continues, even today. Eventually, I suppose, all Christians will be congregations of one. I've seen that attitude expressed more than once here.