I was speaking with a friend when the topic of integration came up. He is ethnically German and told me about how his ancestors came over here in the mid 1800s. They were content to live in enclaves of German culture in and around the Pennsylvania region until about ww1/ww2 when the anti german sentiment prompted them to learn English in a hurry. Here's an article about a Wisconsin town if you're interested in the topic.
There are more than a few parallels with the modern hispanic subculture. I think this totally refutes the melting pot concept, with an important distinction: you can't really tell if someone is of German or English ancestry in the US without breaking out the calipers, but you will always be able to tell if someone is hispanic on sight, even if they have perfectly integrated.
As I see it, Germans were the best case scenario for the melting pot to work out and there are still places today in the US that have not fully integrated, and that was after two world wars with massive anti German propaganda campaigns.
What are your thoughts on the future of Hispanic integration? I think its grim.