But I think the article misses an important point. Namely access to venture capital money.
Put it simply, it's much easier to raise a lot of money for a startup (especially an early stage one) in the US than in Europe. So European companies often operate on a shoestring budget in comparison to the US counterparts. Heck, many of investments I've seen for UK companies wouldn't pay for a single engineer in the valley. Or at best, they leave a lot less cash available for marketing later.
Just seems like there's less access to money or a support network in Europe. So as a result, US startups can operate on a much larger scale.