Americans like scoring. The long TD pass. The booming home run. The blazing slapshot. The ridiculous dunk. Soccer offers none of these. There might be one play that is comprable to these in a soccer game, and the score is still 0-0 or 1-0.
The NHL eliminated ties and put rules in place to allow the star players to shine. The league is growing. I think soccer games would have to see at least 10-15 goals a game before American might get interested and where it might overtake the NHL for 4th place among the big 4 American sports. But otherwise, soccer is always going to be a niche sports among Americans.