The World's Tallest TOWER, period, is near Blanchard, North Dakota. The KTHI-TV tower is 629 meters (2063 ft) high; its neighbor, the KXJB-TV tower in Galesburg, ND is 628 meters (2060).
The CN tower is a "structure" but far from the tallest "tower". The Aussies will dwarf them all, however. Pretty cool.
It said "tallest free-standing structure". The radio masts in ND are not free-standing, and I believe the tallest radio mast in the world is currently somewhere in Poland.