The rubber stamp Congress for the left in the US gave you the great society reforms, and Medicaid is still in place as a safety net for a huge number of Americans, and has been for 60 years. Even if the system is imperfect, it’s had a massive positive influence on the lives of Americans who’ve suffered under the current medical system. The point is that there hasn’t been consistent support for democrats over a number of elections since — Obama, Clinton and Biden is all there’s been over the past 60 years, so it’s clear that the American electorate that votes, both inside and outside the Democrat party, prefers republicans or republican-lites. So you end up with republican-lite or fascists because of apathy.
For a UK example, until recently the triple lock on pensions has sat untouched for far too long because it was considered electoral suicide to try and prise money from pensioners grasp because they vote consistently, despite broad consensus that it was a good idea.

+1. Organise and vote — don’t just do one.