I feel like what you are touching at is that liberals in the US, and Americans in general, are waiting for a touch stone. So far nothing has gone so far as to start the fire. On the other hand there has been no centralizing ember, someone to carry the torch.

Yes, the US has a long history of minority organizing, but minorities are one of the worst groups for turning out for elections (in fact minorities are more likely to turn out if they are voting for Republicans than they are for anyone else, a key element of being a conservative in the US is turning out to vote but liberals can’t seem to harness that energy).

The US doesn’t have the baggage as you mentioned, but the existence of the two party system carries a ton of baggage on it’s own and has effectively squashed most third party resistance.

Most American’s do believe in Democracy, but sadly one half is too stupid to know what it is and the other half only believes in it when it supports their ideas. The second group is one which would happily ban all abortions and then complain when a woman can’t get an abortion even though the pregnancy is killing her. My very own cousin is white trash poor with his children living on government assistance, but thinks we need to end welfare because the minorities are using it. These people are too stupid for governance.

To your final point, the US left needs a leader, a cult of personality to combat Trump, but there frankly isn’t anyone right now. So far no one high enough up in the social circle has been willing to stick their head out far enough to rally around.

I hate to say it, but the US is at the point where we need a life line. Just like the US coming in and occupying Germany to eliminate the Nazis, we now need an outside force to help fix our shit. Short of that the US needs another civil war, but I’m not so certain that it will go the way we want it.