I don't think that the 27+ EU markets are a problem. I'm not even sure if there are 27+ different markets in the EU in the context of startups/tech, because if there were then each country would have their own isolated tech ecosystem which is not the case. Most EU countries are dominated by US tech companies.
If different cultures and languages are not a problem for US startups in spreading to Europe I fail to see why it would be a problem for EU companies