I am going to guess it is just familiarity with the names (and perhaps the American announcers don't want to invest the time prior to each game).
This is the World Cup! Why wouldn't their bosses demand that they invest the time needed to do their job correctly before each game of the sport's most important competition? Would Fox's NFL announcers be given a free pass if they were to refer to "Ben RETH-lis-berger" or "Colin KAY-per-nick"? OK, maybe not Colin, since they probably are told not to mention him at all.