Ever since the dollar cemented its role as the world’s dominant currency in the 1950s, it has been clear that America’s position as the sole financial superpower gives it extraordinary influence over other countries’ economic destinies. But it is only under President Donald Trump that America has used its powers routinely and to their full extent, by engaging in financial warfare. The results have been awe-inspiring and shocking. They have in turn prompted other countries to seek to break free of American financial...