PARIS – Like brothers in arms united in combat but divided in peace, Europe and the United States, which had fought depression jointly in 2009, started voicing disagreements in 2010 and begin 2011 with divergent positions on macroeconomic policy. The price of divergence could be steep: though the worst is over, effective coordination of policy is still needed at a time when rebalancing the global economy, as the G-20 has called for, is far from being accomplished.