Seth Klarman, founder of $30 billion hedge fund The Baupost Group, is concerned about growing nationalism in the US and abroad. Klarman says investors should be worried. President Donald Trump "puts the U.S. at risk of both grave strategic miscalculation and reduced global influence," he wrote, which could undermine markets. The founder of one of the world's largest hedge funds says the global political climate poses a grave threat to democracy and international markets.