I find US politics wild. How is capitalism vs Marxism not a right/left split?
For us left means "liberal", though with again a different definition that isn't rooted in liberty, or " progressive", which is a horribly confusing term that seems to imply you believe incremental change is always the best approach.
Right here means "conservative", though again the definition there has gotten confusing over my lifetime.
I think its a fair argument, though, that because we have been capitalist from the beginning and don't have any history with communism in our system, the traditional left/right split is less helpful here.