KAZAN, Russia — Australia dominated the 100-meter backstroke events at the world swimming championships Tuesday, winning the men’s title and going 1-2 in the women’s final. Two more world records fell — including American teenager Katie Ledecky for a second consecutive day — on the third night of swimming at Kazan Arena, where a cool breeze swept through the soccer stadium. Mitchell Larkin, who came into the championships with the top time in the world this year, won the men’s 100 back in 52.40 seconds. “The first thing that came into my head was, ‘Wow.