When a president speaks, others hear. When he acts, he sets in motion a chain of reactions. When he selects one option, he precludes others.

This is why presidents are surrounded by elaborate staff systems to help them--and oblige them--to think through their words and actions.  

If we impose tariffs on Chinese products, how might they retaliate? What's our next move after that?

If we want to pressure Iran more tightly than our predecessors, what buy-in will we need from other countries? What will they want in return?

What do we want from North Korea that we can realistically get?

Team Trump does not engage in exercises like this.

Team Trump does not do it because the president does not do it. His idea of foreign policy is to bark orders like an emperor, without thinking very hard about how to enforce compliance or what to do if compliance is not forthcoming.

The administration canceled the Iran deal without first gaining European, Chinese, Japanese, or Indian cooperation for new sanctions.

Trump started a trade war with China without any plan for response to the inevitable Chinese counter-moves.

He enthusiastically pounced on a possible U.S.-North Korea summit in the false belief that such a summit represented a huge concession to the United States rather than--correctly--a huge concession by the United States.