When Major League Soccer started play 22-years-ago they didn’t follow the rules that most of the rest of the world were using. One such example is that their clock counted down instead of up. This was in an attempt to align themselves with other American sports instead of playing football (soccer) like the rest of the world does.
Starting in 2005, MLS adopted the rules from the International Football Association Board (IFAB). People often mistake FIFA as the governing body over the laws of the game. That said, FIFA represents half the voting members of IFAB, but they are separate institutions.