CAMBRIDGE – As the global economy stabilizes, there is a growing danger that the United States and China will slip back into their pre-crisis economic patterns, placing themselves and the rest of the world at risk. Despite Chinese official rhetoric about the need for a new global currency to replace the dollar, and US lawmakers’ flirtation with “Buy American” clauses (which scares everyone, not just the Chinese), no one will want to rock a boat that has almost capsized.