Other people have already posted good answers so I just want to add a couple things.

If you want a very simple, concrete example: Healthcare. It depends on how you count, but more than half the world's countries have some sort of free or low cost public healthcare, whereas in the US, the richest country in the history of countries, that's presented as radical left wing kooky unrealistic communist Bernie idea. This isn't an example of a left-wing policy that we won't adopt, but of what in much of the world is a normal public service that we can't adopt because anti-socialism in this country is so malignant and metastasized that it can be weaponized against things that are just considered normal public services almost like roads in other countries.

A true left wing would support not just things like healthcare, but advocate for an economic system in which workers have control over their jobs, not the bosses. That is completely absent.

Also, this meme:

It's glib, but it's not wrong. Both parties routinely support American militarism abroad. Antimilitarism in favor of internationalism has been a corner stone for the left since the left began.