GENEVA — European nations agreed Thursday to boycott the World Cup and all other FIFA competitions to protest Gianni Infantino’s plan to sell stakes in soccer’s biggest tournament to private equity investors. The next scheduled FIFA tournament is within weeks in Europe — the Women’s Under-20 World Cup hosted by Poland from Sept. 5 — and the four British federations comprise FIFA’s only bidder to host the 2035 Women’s World Cup. “The FIFA World Cup belongs to football. It also questioned the need for outside investment “following the most profitable FIFA World Cup in history.” In a video message published Wednesday by FIFA, Infantino insisted spinning off its money-making operations was “an offer, not an obligation.”