This financial powerhouse is winning with younger users.If you thought companies like American Express, Goldman Sachs, and JPMorgan Chase were behind the digital curve, think again. These three companies are 175, 156, and 154 years old, respectively, but they're all part of the digital technology revolution. They're competitive with the newest and most innovative fintech companies, but they come with the stability of more than a century of financial management.I want to focus on American Express, which has ...