Far too often I think people apply traditional North American sports thinking to MLS and sometimes you just can't.
1) MLS clubs can win Conference titles, MLS Cup, US Open/Canada Championships, Supporters Shield, Champions League.... and probably even more trophies going forward (Anglo-American Cup, SuperLiga are both on the radar). So there's a lot of trophies for teams to win between winning MLS cups and I think that will sustain fanbases nicely. We saw Philadelphia nearly win MLS Cup. RSL and Montreal nearly won Champions League. The fanbases showed strong support of both of those competitions.
i disagree...only MLS/ US open cup/ concacaf champions league excited people ( man would say two of those three dont but should) anything else is more like friendly/ preseason cup so not many people care.
heck, look at all the "rivalry cups" that exist. outside the cascadia cup...are people really excited to have won the "cup" no. they are excited and happy to beat your rival in each game not that you won a "cup".