history, tradition and national identity and pride. The US is not civilization-state and doesn't have its own language (which is a very important component in a civilization). Its history is too young and too straightforward in its development (not very storied comparing to 1000 years of Russia and 4000+ years of China) and people in US are struggling in finding national identity.
You're a psychologist if i remember it correctly. You certainly understand your jealousy and self-hatred.
Btw, neither Russia nor China is monocultural. Muslim accounts 20% of Russian population, much more than that of U.S.. you would be amazed to see how diverse China is if you go to china. It is not uncommon that a person from one province doesn't understand the other person from another province in China even they both speak Chinese.