Woodrow Wilson (1913-1921)
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Woodrow Wilson is the third most influential president of the USA and all for the bad.
He perpetuated racism by firing all African-American officeholders he could.
His record of meddling and intervention in the Caribbean, Mexico and Latin American causes us problems to this day.
His unnecessary and unwonted intervention in WWI upset the balance of power that had lasted and righted things in Europe for centuries.
His moralistic approach to international policy still persists. His misguided blundering at the Paris Peace Talks settled nothing and even worse, brought us Hitler and WWII, the most devastating historical event ever suffered by the human race.
Even his moralistic campaign to impose his ideas of Anglo-American democratic institutions on those peoples who don't want it or can't use it still persists. (Consider Iraq!)