It's been dubbed the "most predictable crisis" facing the U.S. economy, but an expert has warned it will take a "miracle" to save America from its national debt problem.Nassim Nicholas Taleb, the author of best-selling book The Black Swan, correctly predicted the 2008 financial crash but said "gloomy" times ahead for the U.S. economy are far more easy to spot.Taleb, who advises Miami-based hedge fund Universa Investments, told an event hosted by the organization this week that national debt is a...