The primary component in the success of US banks over European banks is that European banks struggle to do business in the US. This is because the jingoist zeal in the US puts up massive hurdles in the way of any foreign bank.

In other words, Americans only buy from Americans. This is why "Twenty-five years ago, European banks charged into the U.S. They bought storied firms like Donaldson, Lufkin & Jenrette and Wasserstein Perella and dangled big paydays for rainmakers" - to convince Americans they were buying from other Americans.

This allows American banks to build up a war chest domestically and keep the fight in Europe and the developing world - while there is no fight in the worlds largest economy. China is doing the same.