What I think plays a big role is aggression. Startup founders in the US would do whatever it takes to succeed. Sometimes this leads to hard work (80+ hour weeks), other times to unfair play (Uber licensing and traditional taxis come to mind). Generally, in the US there's a "win by all means necessary" attitude, while Europeans prefer their work-life balance and don't "break the rules" too much. All this is based on personal experience and I have no data to back it up.
That said, I see the same difference between northern and southern European nations. Southern ones are more carefree and want to relax. They even have words and concepts around this (think the Spanish siesta). It's part of culture which translates to work behavior.
I think this difference in founders and employees might contribute more to the scale of startups than what the article talks about. I see value in both approaches.