The US were a blank page, with roughly the same crowd starting with the same common goal and aspirations. Europe comes with 15centuries of nationlike structures and history. Latin and AngloSaxons have very different approaches on life and work (particularly visible in the “PIGS” recent controversy...).
As someone said, you cant make the european omelette with nations hard boiled eggs.
The mere facts that the euro bank notes has zero european symbol (because they couldnt find one) speaks for itself. So they put bridges and windows... India has Gandhi.
And in contrast, this thread's point: that attempts to unify disparate cultures via democracy and mutual agreement, celebrating differences, have difficulties and failures when constituents decide to abandon good faith.
The idea that nation states are old, and multinationalism is new is fallacious. It's only post WWII that borders, political control, and ethnic homogeneity are strongly national... Yugoslavia being the most recent example.
I would love to (interested in the topic)
First national exhibition hosted by the Vichy government during occupation: “la France europeenne”. Showing maps of future europe, where nation-states would have disappeared.
French far-right at the time was also calling England, “the enemy of europe”, for instance on a book from M. Déat, another politica leader from the 40s.
"Anglo-Saxons" are not part of the federation anymore, and stuff like "PIGS" is simply casual racism. Do Northern European countries have a casual-racism problem? Very much so. Would that stop a federation from working in the long run? I doubt it very much. Otherwise Texas and New Jersey would have parted ways a long time ago.
Also, comparing diversity is tricky - natives from Lappland have 0 in common with say Greek or Spaniards. Same would go for india's extremes, its rather impossible to say who is more different (personally I would still say Europe, since ways of life are almost the same if you look on India east, south, north, west, very similar cuisine etc... not so much in Europe).
We have proven track of how it doesn't work here in Europe, no need to spin another set of wars to re-confirm it.
Also, India sees quite a bit of domestic terrorism in its eastern parts exactly due to mindsets like yours. Not something we like to see here in Europe.