> A much more likely reason to me seems that Europe is much more diversified in law and culture, a Paris company has a much harder time expanding to London or Berlin than an San Fransisco one will have for Los Angeles or New York. This naturally leads to more, smaller companies.
I am not sure that's the case. The EU car companies had overtaken the US car companies, inspite of the above scenarios.
Or the large companies that are repackaged versions of much older companies, with lineage back to the 19th century. Exxon & Chevron, for example, trace back to Standard Oil (1870); AT&T and Verizon (from Bell, 1877), Dow/DuPont (1897 or 1802, take your pick), Citigroup (from Citicorp, 1812). Banking often goes further back: BofA (Massachusetts Bank, 1784), JPMorgan (Manhattan Company, 1799).
Moving cuts of the pie around is a shell game. For sure the US is less regulated than Europe, so labels change more often, but the old money doesn't.
Top? The S&P 500 is riddled with mediocrities and rent-seekers.
17.5%? Five out of five hundred is 1%.
17.5% of the market share.
Sure, they are no Google or Amazon, but they are or were nothing to sneeze at either
I'm also highly doubtful that this is mainly because of anti-trust laws.
A much more likely reason to me seems that Europe is much more diversified in law and culture, a Paris company has a much harder time expanding to London or Berlin than an San Fransisco one will have for Los Angeles or New York. This naturally leads to more, smaller companies.