This article by Shadi Hamid, published by the Brookings Institution (originally published in the Atlantic) is a must read. It argues that Donald Trump has exposed the tension between democracy and liberal values—similar to the Arab Spring.
Personally, I find the article a bit far-fetched. It almost portrays Trump as an Erdogan type character.
For me, there are two important points to add. Firstly, there are enormous checks and balances in US government. Secondly, most US presidents abandon their campaign rhetoric and concentrate on the politics of power.