PARIS—For two decades, the U.S. dominance of women’s soccer was built on higher investment, superior infrastructure and greater professionalism than its European rivals. Or, put another way, the U.S. dominance was built on many countries across the Atlantic simply not caring as much.

In the multibillion-dollar business of European soccer, the women’s game was an afterthought. But if only a small piece of that revenue could be reinvested in women’s teams, the thinking went, the whole balance of the game would change.

Well,...