"its (the US) diplomacy, military might and willingness to engage in free trade have underpinned a global system which has been largely peaceful and has fostered prosperity."

Not quite.
Actually, the 70 years post WWII have seen the realization of FDR's major fear - the takeover of governments throughout the world by global corporations that love war for profit maximization; that see democracy, human rights, national sovereignty, and citizens of every nation in the world, as impediments to profiteering.
  There's actually been almost no peace but endless war.
   As for prosperity, we now realize 90% of prosperity is being shoveled up to the 1%.
   But in the big picture, blaming Trump for all the ills of the world is a very old trick to distract from the enormous corruption of the established oligarchic order of 1% rule which makes survival very difficult for the large majority of people all over the world.