I haven't presented a "straw man," you are moving the goal post.
Left parties exist in the US, their ideology and goals are essentially the same as those in Western Europe and other parts of the world. The Communist Party of the US is recognizable to members of the Communist parties in the UK, France, Germany, etc.. The difference is that there is very little support for that ideology in the US. They are "fringe" only in their level of support, not in their doctrines being "weird" or held by cranks. (Although one could make various comments about people failing to recognized the repeated catastrophes brought about by Communist rule and the continued existence of Communist parties.)
No party is going to form the government in the US unless it has substantial backing among US voters, and Communists don't have that. Despite that they will keep trying. Despite their limited support they have been far too successful in influencing politics and values in the US. The US may yet face disaster because of it.
Both Americans and Europeans value freedom and equality. However Europe has generally stressed equality, and Americans have generally stressed freedom. The outcome has been a number of social differences that have persisted till now. We will see what the future holds. If it makes you feel better I'm not overly optimistic.