Things like making sure medical issues don't bankrupt you is left of center regardless of the system (at least slightly, and it is a policy that has been proven to be advantageous for countries at large), but the US conflates them with large scale nationalizing of industry and removing the freedom to have private property. Taxing Billionaires for a substantial amount of their wealth is also left of center (and something the average person would benefit greatly from). Both of those things are what socialists are advocating for, and with good reason.

But none of it is extreme left. USians cant even name extreme left positions anymore. Extreme left would be nationalizing Silicon Valley and putting them under UN control, it would be dismantling private health insurance completely and using their funds to create a nationwide system like the NHS (without being starved like the NHS). It would be a tax rate of 100% for every income (including non-realized wealth growth) above a certain amount to finance public services.