There is a lot of anti-establishment sentiment in the U.S., but what I think outsiders don't understand is that it's fragmented between the parties. Many anti-establishment, working class people are socially conservative as well, and vote Republican. They have no place in a party that talks more about race and sexual orientation than about immigrants taking American jobs. By the same token, many progressives are social liberals first and foremost. For them, opposing second trimester abortions is a bigger sin than working on Wall Street. That divide exists to an extent even within the Democratic Party--most of the "progressives" I know hate Sanders and think he's a "racist" and "sexist" "old white man."
This means that a key progressive premise--the idea that if the party only moved sufficiently left voters would "turn out"--is a mirage. Yes, there's a lot of anti-establishment, apathetic voters out there. There was a huge surge in turnout in 2020. But out of people who voted in 2020, but not in 2018 or 2016, fully 47% voted for Trump, versus 49% for Biden: https://www.pewresearch.org/politics/2021/06/30/behind-biden.... There is just about zero chance that any of those Trump voters would have turned out for any of the progressives apart from Sanders. (But, as discussed above, Sanders couldn't carry the social liberal wing of the Democratic party that Biden carried.)