The Matildas are currently involved in a serious dispute with Football Federation Australia over compensation. The majority of their senior squad is on strike, leading them to withdraw from the victory tour.
US Soccer has been aware for a few days now of the situation and was working to find a replacement opponent rather than cancel the matches.
The United States will now play CONCACAF opponent Haiti, who they last faced October 20, 2014 during World Cup qualifying. The U.S. beat Haiti a resounding 6-0 in that game.
Haiti is ranked #63 by FIFA compared to #9 Australia, but it's worth it to remember that Haiti is also a small nation and its women's team is perpetually underfunded and undersupported by its federation.
Fans in Detroit and Birmingham are probably in for games as lopsided as the USWNT's last wins against Costa Rica (8-0 and 7-2) but for a victory tour, it's probably fine for another couple of games to get played as pure entertainment before head coach Jill Ellis turns her eyes towards an Olympic qualifying roster.