For starters, it's helpful to remember that Americans have overcome great obstacles in the past, when many doubted success. The American Revolution, the Civil War, and the great world wars easily come to mind. They point to a can-do ability that supersedes circumstances.
Despite talk of two Americas and the popularity of secessionist petitions (hundreds of thousands of people have signed them for every state in the Union), it is inconceivable that there will be a repeat of the Civil War. Similarly, the probability of a great-power or global war is virtually nil.