An american anime geek does not have more in common with a japanese anime geek than an american evangelical. Race, nation, language, history, etc are far more potent than what naive utopian people wish it were.
Communists used to think like you. They felt that a german factory worker had more in common with a french or russian or chinese factory worker and that introducing communist ideas would let awaken them to this "fact" and they wouldn't join the army to kill each other. WW1 and WW2 proved that german, french, russian, chinese, etc factories were more than willing to kill each other by the millions.
The geek thinks, ‘Meh: here, Canada, London, Japan, Singapore—as long as FedEx can reach me and there’s a good Internet connection, what’s the difference?’ (Nor are the technically-inclined alone in this.8)
I guess the "geek" hasn't tried to getting visas or immigrating to those places.
Also, you have to realize that all it takes in just one nationalist movement to spur nationalism almost everywhere. Nationalism has that kind of virtuous cycle.
Look at the current US-China trade war. It not only increases nationalism in the US, it also increases in China.