For Trump to deliver his promise, he has to start with easy ones, like scraping TPP , green light for Keystone, etc, causing no disturbance.
But modifying NAFTA would be a tough one, not sure if he can get it done before his term ended. Negotiating a trade deal usually takes very long time, like TPP took almost 10 years.
Let alone other stuff, like building wall against Mexico, trade negotiation with Japan, etc, trade war with China, etc. They will be much tougher and time consuming.
To attack in all fronts, Trump will stretch himself too thin to gain anything, or simply collapse.