Bernie Sanders would be a very moderate Social Democrat in most of Europe, slightly left of center. The fact that he plays a very small role in US politics and is obstracised as some kind of SuperStalin is telling on where mainstream US policy is on the spectrum.

Name a SOLIDLY left wing party with significant representation in Europe so we can put your reasoning to the test - people like you love to deal in generalities so you don't have to be nailed down on your sweeping statements, so show us some examples. Then we can pick a few policy issues and compare.

If I read https://berniesanders.com/issues/ all points except immigration and the green new deal would be considered quite right wing points in denmark, not just a little bit to the right of center.

I just read all of the Danish party platforms and I find them incredibly right wing compared to US ones, so there you go. My anecdotal evidence wins.