From the Economist:
The international tax system has long suffered from two related problems: firms go to great lengths to book profits in low-tax jurisdictions, and governments thus have strong incentives to compete with each other in cutting levies so as to attract investment [only a dirigiste would consider this a problem]. Hoping to forestall a [competitive] race to the bottom, 136 countries reached a [collusive] compromise in 2021 to overhaul tax rules—the outcome of talks held under the auspices of the OECD, a group of mainly rich countries. The crucial element was that governments would impose a minimum tax rate of 15% on the profits of multinational companies.
...Unlike America’s withdrawal from the World Health Organisation and the Paris climate agreement, the OECD framework is not a formal treaty that America can leave. Rather, it is a common approach that depends on governments each passing legislation to impose top-up taxes on companies that pay less than the 15% minimum. This means that, if some countries choose to tax a multinational firm at a lower rate, others can claim the difference.In other words, if the US doesn't tax its corporations at 15%, foreign countries can claim the difference.
...Mr Trump hopes to break this logic by promising brutal retaliation. Any country that imposes a top-up tax on an American company would, in his administration’s view, be guilty of extraterritorial overreach. In executive orders issued on January 20th, the day of Mr Trump’s inauguration, it said that it could respond by doubling taxes on citizens and firms from any offending countries. These orders displayed his advisers’ talent for unearthing obscure statutes that serve their goals: the law that allows the doubling of taxes on foreigners has been in place for nine decades without being used. Even if Mr Trump’s objection to the OECD deal was expected, his threat’s ferocity surprised observers.