To be more specific, there were generalized regions and not specific data centers. Americas included North America, South America, and Australia. Asia included Korea, the Pacific, and Japan. Europe includes Europe and the Middle East. (There is also the China region, but that is not on BattleNet, it is operated by NetEase.) Each region included at least three data centers and even then you were connected to the data center that has the best latency in most cases (the only exceptions are if you play during a low-peak hour or you are a very high-ranked player). The Global Play system we have today simply no longer separates by region in terms of matchmaking, which you can learn why this happens here: