When President Obama visits China for the first time on Sunday, he will, in many ways, be assuming the role of profligate spender coming to pay his respects to his banker. That stark fact — China is the largest foreign lender to the United States — has changed the core of the relationship between the United States and the only country with a reasonable chance of challenging its status as the world’s sole superpower. The result: unlike his immediate predecessors, who publicly pushed and prodded China to follow the Western model and become more open politically and economically, Mr. Obama will be spending less time exhorting Beijing and more time reassuring it. But the Chinese were not particularly interested in the public option or universal care for all Americans. Obama has struck a mollifying note with China. obama is now working on something to fix this major problem.