The accepted proper American English is the accent of the southeastern midwest. Only a few million people speak it, out of the 310+ million people we have now. We're the third largest country in the world, so differences in accents are an obvious given, and there can't be a one size fits all narrow, standard language for that many people. If my parents teach me Bengali and all my peers have a stereotypical Philadelphia suburbs accent, then which one will I speak? "Proper" Bengali, or an anglicized version? I can talk like a native Bengali speaker, but I know people who can speak Bengali better than I can but only with an anglicized accent. It's not a big deal because you'll pick up the accents of the people around you. The accent you have is also not set in stone. There are several thousand sounds you can make with your mouth, but most people use less than a hundred, so they have the same accent in every language. I'm learning French, and while I started out with an anglicized accent, it's slowly becoming a mixture of Parisien and Québécois. That's only because I've been talking to native speakers recently, while before I only had access to teachers in American schools. I'm jumping right to a natural accent in Russian by only practicing with native speakers who actually live in Russia.
I'm what most people would consider cultured (speak three languages really well, learning several more, Skypeing with people around the world, learning how to sing Russian folk songs, etc.), but even I have to agree that the culture studies classes in American schools are BS. You don't really learn anything from them except the white man is the devil and everyone else is awesome. If you really want to promote cultures, you're better off making all of your students have long term pen pals in at least three different continents. That would do a lot more than any culture studies class.
