I agree with the sentiment, but I don't believe the US has any meaningful 'extreme' left. Far from a definitive source, but experts do seem to agree that the Democrats are moderates, not the far-left liberal party they are depicted as. Republicans are an extreme right party, though.
So to the spirit of your statement, yes I'd like to see essentially the DNC platform of today implemented as a minimum-positive-progress platform to improve the country. But IMO those are table stakes for a declining democracy to tackle, not some 'liberal' platform. I'd love democrats to present a truly liberal platform to bring the conversation out of the extreme right where americans are brainwashed to argue whether we want all citizens to be able to afford basic healthcare.