Trump announced he was expanding the product coverage of his national security tariffs on STEEL and ALUMINUM to include "derivative" goods that use steel and aluminum as an input - eg, steel nails or aluminum bumpers.
whitehouse.gov/presidential-a…
Economists call this "cascading protection."
Trump's tariffs on inputs lead to higher costs for US companies making the downstream products, and this results in a clamoring for ADDITIONAL trade protection for those products.
This was all completely predictable.