If we disregard the rare example of trying to avoid a scheduling conflict in another continent, such as a major sporting event that might keep audiences away during a certain time period, there is an obvious, deliberate business decision at play here. The trend is growing, and there are a number of reasons why.
First, it's an effort to combat piracy. By letting other countries legally see blockbuster American motion pictures first, the way they were meant to be seen in theaters, the demand for illicit copies of the content will hopefully be quelled.
Second, it's an opportunity to build buzz before the movie opens State-side. Already we're hearing about how much money Iron Man 3 is making with Chinese moviegoers. Americans who tend to line up to catch a film during opening weekend already are starting to feel left behind and will hopefully flock to the theaters as soon as it's available, and those who typically wait a few weeks might change their minds and buy a ticket sooner.
Third, and the most blatant reason, is to make more money. Studio films are often making more than half their box-office income from the overseas marketplace. Show business is truly becoming global. The domestic biz is still very important, but Hollywood is doing everything it can to capitalize on the international demand and maximize its profit margins.
There you have it. We will likely see more and more movies premiering elsewhere before coming to our shores where they originated. As long as the wait isn't too long, it's just another part of the game of moviemaking that we'll have to get used to experiencing.