One aspect of MAGA is isolationism.
Let's look at that economically. Trump promises that if we abandon NAFTA, CAFTA and other trade agreements that factories will move back to the U.S. and we will all have chickens in every pots and abundant jobs. It's not that simple. First of all, when factories move back and rebuild they add technology and robotics that eliminates many jobs. The factory comes back, the jobs don't. Secondly, NAFTA has raised the standard of living in Mexico--and Mexicans aren't immigrating here. Central Americans are, because they have not yet benefited with a higher standard of living. If we had never had NAFTA our immigration situation would be more unmanageable. NAFTA had good effects and bad effects.
To say that economic isolationism would change things back to how they were is unrealistic.
Similarly with climate change and the Paris Agreement. So what if China isn't addressing climate change as quickly as the U.S. would like. Will our thumbing our noses at them and saying, "We have the right to produce just as many greenhouse gases as you, nah-nah-nah-nah!" help? It's called "global warming" (and ocean warming is the biggest contributor to our problems) for a reason! Every country has to do as much as possible and if we do nothing in a fit of pique we are making the situation worse...