Late Stage Capitalism

Sorry but no. The far right is on the rise globally, and as much as Muricans want to feel self-important, their cultural and political export has not yet reached a level where the actions (or in this case, inactions) of a domestic political party that doesn't even really align with any other party globally (given Dems consider themselves leftists when compared to actual alignment based on policies, they're firmly center-right to right), are not a direct contribution to it.

No, for example, the right rose in Europe in the wake of the immigration crisis starting ca. 2010 (compounded with the global crisis of 2007-08, which admittedly was caused by the US financial market), which in turn is a result of US interventionalism in the Middle East for the past, oh, thirty years (well, it was about 30 years in 2010), but especially the ramped up failed wars since 9/11, that only managed to destabilise the area enough so that a large swath of people would pick out whatever remained of their lives from the rubble and move towards the EU in hopes of a better, safer life.

That combined with the sitting, mostly center-left governments' complacency in most EU countries, has led to a major humanitarian crisis that left the poorest of most EU countries' feel neglected, and now that same layer was enthralled by the far right, that used the ongoing support of immigrants as the kernel of truth in their web of lies, convincing swathes of people.

So no, the Dems not being leftist enough isn't the reason the far right is on the rise globally. It hardly even contributed to it since even the most leftist presidents have continued to bomb the shit out of the Middle East. And when two-term presidents can't even wrap up wars their predecessors began in 8 years... that's not a policy issue anymore. That's straight up the system keeping the wars going because they're profitable, and no amount of extreme leftist policy is going to take that trash out.