United States House Speaker Nancy Pelosi's contentious visit to Taiwan this month laid bare one of the fundamental dynamics of the American political system that often goes underappreciated by outsiders: that Congress and the White House are co-equal branches of government which do not necessarily act in concert with each other, even on foreign policy.

The fact that Mrs Pelosi's visit went ahead at all, in the face of public misgivings by the Biden administration, shows the limited leverage the President has over Congress, even one controlled by his own party. By design, the White House cannot "rein in" Congress on Taiwan or any other issue, no matter how much Beijing might want President Joe Biden to do so.