What did President Trump do on his first day?
Well, he started with "breakfast" with heads of major businesses in the Roosevelt room. A breakfast of sour grapes, bitter pills and some coffee for them to wake up and smell - no actual food was served. Trump told them to get their jobs out of Mexico PDQ because it turns out the wall is going to stop manufactured goods as well as illegals. He probably created more jobs for Americans there and then than Obama did in eight years.
Next he dropped into the Oval Office and revoked the Trans-Pacific Trade Partnership (TTP). The TTP has been brewing since 2008 and was basically agreed in 2016, but now it is stone dead. He hasn't done the same for the Trans-Atlantic Trade Partnership (TTIP) yet - it is less advanced than TTP and not due for ratification until 2020, but most likely Trump will kill it in due course as well.
So excellent news for America. Less so for other countries, especially Mexico which stands to lose both a hanger full of jobs and billions in remittances from its ex-pat workers in the USA, not to mention forking out to pay for the wall as well.
The UK has a major trade imbalance with the USA, in the favour of the UK, to the tune of about £40bn per year (which more than offsets our annual loss of £23bn with China.) Fortunately Trump has said that the UK will be "front of the line" for trade deals with the USA so his protectionism should pass us by. Also we export all sorts of intangible stuff like financial services and software which no wall is going to stop.
After sorting out trade Mr Trump decided to implement "small government" by declaring a federal employee hiring freeze - no positions vacant at noon on the Jan 22nd may be filled, except for military.
Then he had lunch.