I think the american fanbase was the worst considering how we are raised to have no such things as humility, empathy, and minimum of objectivity and to believe we are the best of the best and be proud of something that was build by others and we become arrogant like hell.
One Piece needs a required taste and to be able to look past the wackiest traits of the series. The average american teenagers would get turned off by the series. Oda actually gives enough moments and developments to all the potential ships to make them all believable as well. I ship Luffy Nami but strangely enough I don't really mind Nami Sanji. I think Kishi made a mistake of trying to bury Hinata because she was becoming too popular which backfired by making SP and her fans more hungry for her. He should have given her moments and make Hinata and Sakura interact as friends and the whole retrieving her heiress title as her arc and make Neji Hinata more obvious. In addition, Oda still has a lot of major loose ends to tie up that are more thrilling and engaging than the shipping war. Let's face it, the war arc was dog kitten and way too long and the end pairings were the only loose ends that kept the fans interested and things got even worse when Kishi was letting his fans control his series. There were no real exciting battles to come except Naruto vs Sasuke with cheaply boring recycled zombie enemies or loose ends to resolve and the better one was intentionally left unresolved to change the ending. When the final war of One Piece is gonna come there will be still a lot of loose ends to tie up and actual exciting battles to look forward to such as the will of the D, Luffy vs Blackbeard, Zoro vs Mihawk, the will of the D, Shanks' past, Dragon's past, the true history, and so on. There is barely any chance that the pairing wars will overtake the climax of the series. Overall, the series has remained strong for the past almost 20 years which is unbelievable.