American social media companies have the benefit of a large homogenous deeply interconnected culture with a vast ad buying community. Simply put, a U.S. social media platform can get more revenue with less effort than a European counterpart (because they have to go country by country, language community by language community), and will generally outcompete those EU counterparts, with social network reinforcement effects doing the rest. This holds up for most ad-supported online services, which together with a much stronger private investment sector is the reason American platforms absolutely dominate Europe. The EU has a stronger government subsidy system for software but that system does not reward or expect market success, which is why it delivers very little value.