The 21st century and especially September 11, 2001 changed this state of affairs: the powerful America revealed its flaws, highlighted by the financial crisis of 2008. Challenged in their external operations, from Baghdad to Kabul, the United States under Bush and then Obama will carry out the "American withdrawal " while China under Xi Jinping asserts its desire for hegemonic power. Donald Trump's presidency is yet another step: between America first and contempt for multilateralism, the United States is disappointing its historical allies. With the election of Joe Biden, can America still make its great return?