Looking at history, we can see that shortly after the great stock market crash in Oct 1929, tariff walls started going up all over the then industrial world (I believe Europe-led).  Mr Trump proposes to rip up NAFTA and put the USA behind protective walls (border adjustment tax, for one), has already ditched the TPP, and WTO be damned.  Many observers say the financial markets are overheated and a 'correction' is coming.  10% ?  20% ?  Don't know.  This could be  a recipe for disaster -- and conflict.
Possibly an exemplar of the sports maxim "what goes around comes around".