The official motto of EU is "United in diversity". People change, countries change, language is almost like a living thing - changes every day... To make out a hypothetical assumption (cultural and linguistic unification) and then argue with it... I don't know, does not seem logical to me.
USA started as a bunch of colonies founded by people of different cultures, traditions and language. Some of you think that USA was made for a week, tops. But in reality that was a long and often painful process.
P.S. USA does not have an official language, EU has 24 official languages, Switzerland has 4, Republic of South Africa has 22... So what was your point again, about French speaking German or something?