Here in the northeast, this analysis matches with my observations. Ping!
Here in the Midwest, while there may be some ‘pockets’ with similar experiences to the Northeast, there seem to be more areas which resemble the South and the West. IMHO.
Irish and German immigrants in the mid-nineteenth century, followed by the Italians, the Poles and others later, built urban parishes by the sweat of their brows only to abandon them a century later. At least there was a post-war explosion of suburban parishes and paraochial schools. Interestingly, these were built to handle the big families that within a generation would be reduced to three or fewer children.
Now, Syracuse hands a church built by German immigrants over to the Mohammedans. It appears some 'immigrants' are more equal than others.