Partially disagree. Certain customers/industries require very little localisation. e.g. a startup that sells cloud services to tech companies, can probably do business with virtually any tech company in Europe in English just fine, but this is a niche. I'm not sure if your startup fits that picture, but e.g. an online takeaway service where you can order food from restaurants in your neighborhood, in English, just won't cut it in France. My parents filter anything not Dutch, despite their English being more than sufficient. Language is important here.

More importantly though, the reason I partially disagree is that language is just one thing. I'm using it as a proxy to show fragmentation in Europe, show differences in culture. Yes one can translate, but it's just one of various issues. Take Dublin for example, tons of tech companies are located there because of fiscal reasons, and you'll find sales teams for google, twitter, FB, Oracle etc etc... you have entire teams, localised. I've got friends working in the Dutch teams of these companies. They call Dutch customers, from Dublin, rerouted through a Dutch line so the customer sees a dutch phone number coming in. That's not because these companies love the diversity of these employees, but purely because that's how Europe still works, each country is unique and you can't interface with millions of regular people in their second/third language and expect to be successful. You don't call French people in English to do sales, in general. (of course, plenty of exceptions but they're still a minority). They've got these entire teams set up targetting countries individually because you usually can't do it any other way. Building these teams takes money, US companies can build US teams, decentralised somewhat, and reach a quarter billion people, then use that cashflow (or investment capital) to build European teams. European companies need to establish in a single market of 10-70m people, then use that cashflow or investment capital to do the same in other smaller EU markets. It's doable, which is why we see lots of successful companies worth a few billion. But scaling like that is slower, you have the odds to get acquired by a larger American (or Asian nowadays) venture earlier than scaling worldwide.

It's like you have a school with 1000 kids, and 20 schools with 100 kids, all quite different and requiring their own approach and investment. 5 businesses start selling candy in one of the small schools and one starts in the big school. It's not a surprising outcome the business in the biggest school will likely scale the fastest, having only to implement 1 approach and getting tons of market exposure, and then has cashflow to acquire or outcompete the rest.

Anyway language alone isn't everything, I was just using it as an example. Take something like lunch culture between the Netherlands, France and Spain. Completely different, running a startup in the lunch industry requires entirely different business approaches. The US has tons of internal diversity, but nothing quite like this.

The EU is awesome, it's very flawed but I love the idea of the union and it's benefited me greatly, so far. But when talking about the EU in this context, compared to China or the US, we really mustn't gloss over the fact these are tens of very different mostly small markets with only some standardised elements. (some EU import/export stuff, the euro, SEPA etc...) I think this diversity plays a major role in company's ability to scale. I can't count the number of successful startups in say France, that then failed to establish properly in say Germany. Some American companies can bruteforce success because they already have large business at scale in the US to finance an adventure in Europe.