You can have a single country with multiple languages, USSR, Yugoslavia, Spain, China, India, USE wouldn’t really need to have a single language it’s population would be forced to learn, instead it would probably remain the way it is in the EU, English (and maybe French?) would be “federal” language(s) and member states would continue business as usual in their languages.
That could make sense if all countries were somewhat equal in their political power per population and if everything depended on population alone, but do you really think that Lithuania, Latvia, Estonia and such countries would have a important say in the politics of USE? Romania has 21 million people, Belgium has just 12, but who is stronger both politically and economically? Belgium hands down.
@Flyer already mentioned, Germany accounts for +20% of EU’s GDP in 2016, including UK, so without it it’s even more.
As for France, I haven’t really seen any sparks between France and Germany, Germany is already forming a unified EU army in a way by combining it’s army units with those from Netherlands and I believe even some from Romania and Czech republic. Macron also called for a unified EU army. He is a strong supporter of the “open doors” for immigrants, which Merkel is (in)famous for.
Someone said that USA isn’t a big California or Texas and that is true, however there’s a gigantic difference in how the states in America work and how independent countries in Europe work. States of the USA are not really “independent” countries in a alliance, they are basically regions with a wide range of autonomy, but they are not independent countries with entirely different political systems and goals.
On the other hand in the EU Greece has it’s policies and world view, Hungary and Poland have their somewhat conservative world view, Germany has its liberal worldview with the whole immigrant policy thing, let’s not even mention Sweden, there are countries that are somewhat friendly or neutral to Russia and some that are plan anti-Russian like Baltic countries. Dramatic differences like those don’t exist between California and Vermont or Florida, however, in order for USE to work, the differences between EU countries would have to be lowered to the level of differences between American states and this is where the problem lies, obviously no one in Berlin or Paris will really care about what Estonia or Bulgaria think about USE’s stategic goals, foreign policy, army,etc., instead they will push their own policies.
France is the only counterweight, Spain and Italy are also powerful, all of them combined are more powerful than Germany, but still Germany is the most powerful one, with the most money and the most influence.