I'm not sure there's a very solid correlation on that. It's true that the U.S. has a lot of startups, and also at-will employment, but actual experimental data is pretty weak, and the U.S. has been a technological leader through various routes for decades, not all of them startup-ish. For example, the old-line engineering firms (AT&T, Boeing, Lockheed, IBM, etc.) drove technical innovation for decades, and had much more "Europe-like" working conditions, where working more than 40 hours/wk was uncommon, employees were rarely fired except for gross incompetence, etc.

If anything, the 80-hour/wk and ready firing of employees thing was traditionally seen as a more "mom-and-pop business" type culture, associated with lower-status industries like the family-owned restaurant, not with technology.