A trade war is a series of retaliatory tariffs that escalate as each side demands concessions from the other. While there are some very legitimate reasons to restrict trade (like national security concerns or political disputes) the resulting series of reprisals often have unintended consequences that hurt consumers.
A protracted trade war between the US and China would likely damage global supply chains. This would wreak havoc on markets across the world, but particularly in Europe and Asia which depend heavily on imports from both countries. It could also fuel inflation in both economies, stifling demand for exports and making them less competitive.
Depending on the extent of the conflict, US and Chinese consumers might lose access to certain products, such as clothing, electronics, cars, or raw materials, including metals. The cost of those goods would rise for both consumers and businesses, who may have to absorb the increased price or raise prices on other products to make up the difference.
In addition, a trade war increases policy uncertainty. When companies do not know whether they will have to pay a tariff or how much it will be, they will delay investments and hold off spending.
Trump’s actions might trigger economic retaliation from Canada, the EU and China. These countries will likely maintain their existing tariffs on American goods to match the US levies, and might concentrate retaliatory action on specific U.S. companies that are aligned with Republican states or whose technology the US is trying to disrupt.