So let's say there is tariff on imported oil at 10$ per barrel. This means that US companies will buy oil locally, which means that all domestic oil producers can raise oil prices by 9$ and still be competitive on domestic market. But that means that cost of production will raise for US companies. Reduced margins (or lower profits) will force domestic companies to reduce work force.

As you can see tariffs on imported goods can have negative effect on domestic jobs.