Americans Think Canada Is the Fairest Trading Partner
CFR has a new poll of Americans' views on trade, with some interesting results. In response to the question "Would you say each of the following is a fair or unfair trading partner to the United States?", here is the breakdown by trading partner:

Congrats to Canada on winning this unofficial competition for fairest trading partner! Canada also scored the highest on the question "Please describe the United States’ relationship with the following countries," with 72% saying it was a "friend and ally." Thus, despite what's going on at the highest political levels, most Americans still appreciate Canada.
(For comparison purposes on the fair trade question, I would be curious to hear the responses in a poll of Americans to the question "Would you say the United States is a fair or unfair trading partner?" Maybe the folks at CFR can add that one in next time.)
Another interesting question was "What do you think the next president should do about Trump's tariffs on the following trade partners?" Here are the results:

This is a complex issue, and I'm not sure how to phrase it to get a good sense of public opinion on where to go with U.S. trade policy under a new administration. Asking only about removal of the tariffs leaves some uncertainty about what else would go along with that. Rather than a country-specific question focusing on tariff removal, I might try something along the lines of the following instead: "Should the next U.S. president remove all of Trump's tariffs and then develop a new overall tariff and trade policy?"
But it's tough to capture everything that is going on with U.S. trade policy at the moment in a poll question. Among other things, you have the tariffs themselves, the various trade deals negotiated by the Trump administration, the choice of countries being targeted, the choice of sectors being protected of affected, and the specific accusations and concerns about unfair trade practices. All of it could be reconsidered by a future administration. I'm not sure polling can get at every aspect, though, and I think that to a great extent a future administration is going to have use their instincts as to the details of what Americans want to see here.