The US built itself by enforcing the WASP ideal over the various newcomers.

Integrating the italian immigrants was a pain, nobody speaks french anymore except in some parts of the Maine and Louisiana and I doubt anyone would say that latinos' integration into the national community is a huge success so far.

I'd suggest you read how french as a language was wipped off the face of the British colonies/the newborn US. It wasn't 'hey dude, I know you have your own language, but you know speaking english would be cool too', but more among the lines of 'French is banned, period.' I'm not even going into the whole irish situation, the japanese and chinese cases and so on.

Of course, things are different now, because banning spanish or openly discriminating the latinos would be foolish, but if you think the US were built as a multicultural state, you're fooling yourself.