President Trump likes tariffs. Most economists and commentators dislike them. The so called international rules based order included the World Trade Organisation aiming to reduce tariffs. The WTO however allowed emerging economies and China to play by different rules to the advanced countries. The WTO let countries impose high tariffs and use high subsidies for food and agriculture.
President Trump has a range of aims for tariffs.
His idea of reciprocal tariffs is a device to get tariffs down . Why not make countries imposing tariffs against your exports pay the same tariff on their exports? It might persuade them to agree to getting rid of the tariff.
His penal tariffs on Mexico and Canada are designed to get them to stop the flow of harmful drugs and illegal migrants over their borders with the USA. They may well get them to tighten their borders.
There is the aim to use tariffs to onshore more investment in industrial capacity. It is a change of emphasis from President Biden’s expensive subsidies which distorted trade and may well help onshore .
There is the aim of collecting more tax revenue. That is true, but its net effects may be less than the gross amount of additional tariff money if the policy reduces the growth rate or results in higher domestic prices squeezing real incomes.
Most commentary ignores the fact that the EU is a customs union with tariffs on 73 % of product lines that it imports. It imposes especially high tariffs on food and agriculture where the US is a leading exporter.
Free trade is a good idea, but the WTO has never delivered it. The favourable terms for China has created huge Chinese trade surpluses.