Hours before boarding Air Force One for Brazil, President Obama defended his three-country visit to Latin America with a reminder that the region will play a critical role in helping the United States meet his goal of doubling exports. In an opinion piece in USA Today on Friday, Obama acknowledged some of the criticism that had been levied in his direction about the trip's timing. He opened by saying the United States will continue to "do everything we can" to address the crises in the Middle East and in Japan, even as he departs for Brazil, Chile and El Salvador....