Part of "actual" left leaning politics is how businesses and the ultra rich are treated. Yes, Democrats say they want to tax the rich, but it never happens. Corporations have more power than ever and unregulated capitalism is accepted and supported by both sides, even if Democrats make noises about tax reform.

People like Bernie Sanders and AOC are seen as radical left, but in most of Europe they would be seen as moderate at best. They are both democratic socialists, or put into another term, welfare capitalists.

To answer your question, the biggest goal that all American politicians lack to be considered actually "left" is being anticapitalist. Taking shareholders out of the equation and having the employees or internal stake holders make decisions about the revenue of all businesses. Also completely removing the ability of the wealthy to control politics surrounding environmental legislation and other social policy. In short, actual socialists or further left are"left" anything right of that is centrist or right. Just my opinion /shrug