Aryna Sabalenka took the next step on the road to a rare US Open three-peat, routing qualifier Polina Iatcenko 6-1, 6-1 to join a raft of contenders cruising into the third round on Wednesday.World number one Sabalenka, without a title since her impressive Indian Wells-Miami double in March was in attack mode as she overpowered 160th-ranked Russian…