The problem is not that the left is an illusion and more that there just is no left wing party in the US.
Like you said there is a right wing party in line with most conservative parties in Europe and there is a protofascist party in line with Putin, American Oligarchy and religious extremism.
That doesn't mean that an actual leftist movement or party can't possibly exist or is a mere illusion.
The political system in the US is just purposefully designed not to allow a successful party on the left.
Elections are decided in big parts with money, which inherently favours those with money (and corporations are people in the US for some fucked up reason).
This is by design and not something that is natural or automatic.
I guess our positions are not that different, I just wanted to add some nuance.