If you're not American, one thing that you have to keep in mind whenever you hear "there's large public support in the US for [insert vaguely left-wing thing here] but nothing gets done about it" is that the US's system of government is really only vaguely a democracy. It gives a disproportionate amount of power to conservative rural voters at the expense of everybody else.
This is exemplified in the Senate, which is the least representative legislative body of any democracy I am aware of. Each state gets 2 votes regardless of population, so Wyoming (population ~550,000) is given the same amount of votes as California (population ~39,000,000). Any remotely controversial piece of legislation needs to pass the Senate with a 60% majority. This means that 21 Republican states making up ~20% of the population can block any bill they don't want to pass. Senators are also elected for 6 year terms, which limits how accountable they are to their constituents.
If a bill gets past the Senate, it makes its way to the president, who has veto power over all legislation. The president is elected by electors selected by the states rather than individual voters, and the number of electors is not fairly apportioned either. For example, there are ~728,000 people per elector in California, but ~196,000 people per elector in Wyoming.
In effect, this means that public opinion has essentially no impact on the legislation the US government passes. A 2014 Princeton study ( https://archive.org/details/gilens_and_page_2014_-testing_th... ) found that "When the preferences of economic elites and the stands of organized interest groups are controlled for, the preferences of the average American appear to have only a minuscule, near-zero, statistically non-significant impact upon public policy."
If you're interested in why the system was designed this way, I highly recommend the book "The Framers' Coup" by Michael Klarman.