Indeed most all are, and even the Indians were immigrants at one time, unless the Garden of Eden was in America. And in this predominantly RC area, in contrast immigrants overall, the white Anglo Saxons are the most ambivalent about or resistant to the gospel, besides being overall liberal.
But besides the problem with immigration today, and how it helps the liberals, the stats point out that this is how Rome maintains its percentage above 20% in America.
The white Catholics from the northeast are the least catholic and most liberal in Florida, where the other Catholics are either of Hispanic descent or are immigrants from Latin America or the Philippines or Catholic parts of Eastern Europe or even from Africa or Asia . Just about anybody is more orthodox than native born white Catholics.