At the time of writing this, May 2016, election of Trump seems quite possible. Trump is not the problem. There will always be deluded people and people who fall for catchy slogans. Jefferson, Adams, Hamilton, Madison, were wary of democracy and designed a system of checks and balances. But the system is not working.
The slogan "Make America great again" is the problem. It appeals to the same basic instincts that brought Hitler to power. Remember “Deutschland ueber alles”? Germans felt frustrated and voted for a crackpot who promised to restore their dignity. Doesn't that sound familiar? When people feel threatened their instincts for self-preservation and tribal dominance kick in. When my family is threatened I might also leave reason behind. When a whole nation responds primitively, it is fascism. One could point out that it is only 70 years ago that the USA fought fascism But when the USA entered the war, it was not to fight fascism. In 1942, after Japan had attacked Pearl Harbor, Germany declared war against the USA, thinking that the USA could not fight on two fronts. Roosevelt had never been able to convince the isolationists. The dominant sentiment was "Let the Europeans kill each other as they have been doing forever". Cynics could even say that strategically Roosevelt's timing was perfect. He waited until Great Britain was sufficiently weakened to make the US the indisputable world leader.