That's up to God, of course, but He's done it before, and terrible things are predicted in the Bible. Usually, in the Bible, when things get really bad sin-wise, God steps in to teach a lesson.
In hindsight, that's how the Old Testament writers explained cataclysms. That's also how they determined who was just, and who wasn't, until Job came along.
You are free to believe that God is just waiting to drop the hammer on America if you wish.
As for terrible things being predicted, yes. But in a world where terrible things happened in the past, predicting that terrible things will happen in the future is a pretty safe bet.