Free markets mean that the individual concerns make their own decisions on what, when and where to buy the goods needed in their business or personal lives, not the government or some labor union or corporation.
Ideally two countries would mutually agree not to place tariffs or give subsidies to businesses involved with trade with the other country. In the absence of the perfect agreement getting as close as you can is better than limiting trade or even worse completely shutting it off.
Nobody mentions the jobs involved with handling or transporting goods. Manufacturing itself is only one aspect of an economy. As a general rule the countries with the freest trade have the stronger economies. Freedom equals prosperity.
Trade balances mean nothing. Sooner or later that money will come home. Think of it like a check written on a bank account. Unless you can cash that check it’s worthless.
Every dollar which will now have to be spent for steel and the things that are made of steel is a dollar that will not be spent for other goods and services.
Other goods and services whose providers employ people.
People who, as a result, will have less work.