The U.S. accounts for 10% of Great Britain's trade. Around half their trade is with EU countries. Not much Trump can do the help with that.
The US is Britain’s largest single trading partner however, and that is without any trade deals whatsoever. Imagine how much trade would increase WITH a trade deal. Even if it does damage to the UK economy in the short term, it will be worth it. You can’t put a price on sovereignty, which is something the remainiacs cannot seem to grasp. Other countries have paid a far higher price to gain and retain their freedom. Selling out to control by a foreign power for the sake of cheaper foreign imports is a pathetic excuse for not being able to rule your own country.