They bring manufacturing jobs back to the US from China and other countries.

Modern munitions are more than gun powder and shells.

One of the most important industries we had in WWII that led to our success was the automotive industry. We were able to convert that to tank, jeep, etc. manufacturing very quickly.

Semiconductors will be key to any future war. If China is able to cut us off from 90% of the world's semiconductor and printed circuit board manufacturing by "quaranteening" or even attacking Taiwan, we will be in trouble...unless we have already started building semiconductor fabs in the US. They take a long time to build. We need more of them here, within our borders.

US companies have been shipping technology manufacturing lines, and even research & development, to China to be made there more cheaply than it can be made here. Technologies that China just doesn't have are being handed to them. China can nationalize that technology at a moment's notice, but for now, they are just slowly hiring people from those US companies, and employing them at state funded startups...and R&D personnel are going to work for their giant academic research institutes which are entirely funded by the PRC. Good luck suing one of those entities for trade secret theft. Tariffs keep new product lines from being transferred to China, just so a US company can meet Wall Street expectations every quarter. Tariff's are long term, not quarterly, solutions. China thinks long term; we think quarterly.

Right now, China is analogous to what the United States was in 1935, and the current US is analogous to what Germany was in 1935. Germany had technology (better weapons across the board), but we had the economic and personnel resources to fight a sustained war. The current US has the technology, but China has the economic and personnel resources to fight a sustained war.