Economically-speaking, the US is powerful. But it is not as relatively powerful as it is militarily. This is Trump imagining it is.
For instance, US farmers won't be able to replace Mexican avocadoes and tomatoes easily. Mexico has a better climate for producing them than much of the US. And anyway, American farms are about to lose their principal source of labour (illegal immigration!) so won't be able to grow the agricultural products the US population wants.
It would be comical if it wasn't pathetic and tragic.
Yes, America can reduce its trade deficit by not doing any trade. But it won't benefit.
Duh!