I think it is because there are so many idiosyncratic differences in international cultures and the US, that it may not be worth the risk for a startup to expan

I think it is because there are so many idiosyncratic differences in international cultures and the US, that it may not be worth the risk for a startup to expand abroad. For example, I wouldn't know the first thing about how to start doing business in The Netherlands from a marketing standpoint. I could read all of the books I could stomach, and interview every Dutch-speaking individual available, but that wouldn't be the best use of my time or, ultimately my dollars. I'd probably end up having to pump cash into hiring a US/NL or US/EU relations team to get it going; all the while I probably don't actually have that money.