The US president has limited authority to unilaterally implement tariffs. He would have to claim national security concerns or retaliation to unfair trade practices from other countries. Trump previously imposed tariffs on China due to (well documenented) unfair trade practices. Biden then extended the China tariffs. But Trump would be legally challenged and most certainly lose if he claimed unfair trade practices by every country on earth.
Here's a good video explaining the problems with tariffs. They have lots of unpredictable long term outcomes and are hard to remove once implemented. Apparently there's still a chicken and truck tax on trade between US and Europe that dates back to WWII.
Regarding tariffs this is a complex issue and he has said repeatedly that it’s a negotiation tool. The records reflects that in he expanded US overseas market access with heavy handed negotiations. Most countries are much more protectionist than the US.
Industrial farming with massive soybean exports to China, who can’t even produce 50% of the calories their population needs domestically, is again a very complicated topic.
China is not in good shape and Trump’s first term was a clear inflection point in their trajectory.
So you believe it had nothing to do with a global pandemic and propping up their real estate markets until they popped?
I'll give a policy example against the average person's interests -- his 20% tarrifs across the board will cause approximately 20% inflation and a trade war that will ruin our export markets just like it did the first time. Trump brags about giving billions to farmers because he had to after his policies decimated their markets.