You say those reasons aside, but I think they’re the difference that makes the difference. No practical changes to the Euro tech job market will change the salary discount compared to the U.S. barring a dislocation in the factors you mention.
It’s generally true that the US is more comfortable with variance in outcomes than the EU. This is a cultural thing which also presents legislatively.
this cultural reason for a lot of countries is logical aswell.
for instance, after world war 2, most European counties had to do heavy intervention in their economy to rebuild their country from scratch.
(the dutch and French had wage freezes until the late 50's, Britain had rationing until the 50's, not to mention the insane human sacrifice during the war. Belarus lost a majority of its population during the war for instance).
not to mention everything behind the iron curtain being completely mismanaged for 50 years after being the area which took the brunt of world war 2.
having two oceans between your country and the rest of the world helps a ton in keeping your economy stable and growing, while Europe at that time was turning itself into literal dust twice in 30 years.
It’s generally true that the US is more comfortable with variance in outcomes than the EU. This is a cultural thing which also presents legislatively.