If you want to change the way voting works in the US (and oh boy do I), you first must win an election in the current system to gain enough power to do that.
So many american leftists just seem to ignore that and it makes things very difficult.
Not quite so, ballot initiatives are actually the best bet. They've been successful in local politics primarily so far, but the initial results are promising (1).
You're right, that the closer you get to that core of federal power the more resistance you come up against, but once there's a powerful enough popular groundswell (that is I suppose, and if and not a when) you can move to mass protests, general strikes, guillotines, etc. This is why it's important to talk about, esp. around those who don't really know about it yet.
So many american leftists just seem to ignore that and it makes things very difficult.