I guess America has been failing since before even the Revolution then. Our history is replete with entire regions of non-English speaking citizens with insular cultures and personally I had thought we did pretty damn good. I must be wrong though.
What worries me a lot more is the intrusion of religious leaders into political matters and the rather sizeable percentage of people that claim to be Christian (or Muslim, etc.) first, US citizen second. When a sizeable portion of our society doesn't identify themselves primarily as US citizens first then we are doomed.
We had small pockets of first generation immigrants who spoke different languages, but by the second generation, they had started to fully assimilate.
Those who did not assimilate separated themselves from society (Amish is a good example).
The religious has ALWAYS, since the beginning, tried to intrude on government. Hell, the prohibition movement was led by the religious. The entire Victorian culture was influenced by religios views on modesty and "decency."
And yes, this is what I mean. Diversity of culture to the extreme point that people no longer have a common national culture and identity. Hell, a large portion of the Mexican immigrant population even calls for taking the South-West back to Mexico. The simple logic of why they came here is the first place fucking escapes them.
There was a time when people came here and wanted to be Americans. Now, many come here and for some unfathomable reason, wish to turn this country into the shitholes they came from and refuse to assimilate. And even those who have been here hundreds of years reject mainstream culture for self deprecating and self destructive culture that rejects any and all things that insure success.