The thing is, we have never had just one culture. We may be predominately of European origins, but this country has always been made up of people from multiple different backgrounds living together for better or worse. You cannot say we have always had a monoculture when people lived in the de-facto slavery of the sharecropping system until sometime in the 1950's, or when there were laws to disenfranchise them due only to the color of their skin or being non-European. Yes, we do need more unity under common principles, but don't be deluded into thinking that this has ever been the norm in America. Remember that the white European experience is very different from that had by people from Africa, China, Native Americans or Japan for instance who were segregated and discriminated against in various forms until very recently. Part of what makes this such a great place now is that you can be who you wish to be without threat of government interference in your life for the most part. That is something we can all agree on and all should strive to protect. Should English be the national language? I tend to believe it should for conducting business with governmental organizations and such. For personal business, it should be up to the individual what language they speak and who they associate with. So far as housing goes, I want to see fair housing laws remaining in effect but would hope that those who wish to do rental business would realize that it is not in their best interest to discriminate against a paying customer.
Do we need to move beyond superficial judgments of others based on external appearances? Yes we do. How we will do so will depend on the choices we make as citizens and what we teach the next generation.