The world owes US President Joe Biden a debt of gratitude for the past three years. But the Biden dam is breaking, and the next year - and probably the years after that - promise to be a whirlwind for US foreign policy.
In the 1920s, the United States was positioned to assume global leadership, but Congress refused to do so; the ensuing chaos in Europe and East Asia led to another world war. Today, the U.S. is still capable of leading, but it is oscillating between constructive engagement and destructive withdrawal.