To attibute it all to lack of ethnic identity overlooks the very important factor of spiritual change. People don’t change religions because they just don’t feel that Italian any more.
Cradle Catholics who never got Catholicism at some point stop going to Catholic churches, because the Church asks of them things they are not prepared to give. This is not spiritual change, it is spiritual lazyness.
There is some truth in what Annalex is saying. 40 years ago, if someone named Czanecki told anyone, especially family, that he was now a member of the Assembly of God, they would have been shocked and mocked him as a “traitor”, even if they themselves were not very religious. This has changed due to assimilation.