Down 23%, is this Warren Buffett dividend stock undervalued?

When one of the world's greatest investors puts nearly $45 billion into a single stock, people pay attention. Warren Buffett's Berkshire Hathawayowns 151.6 million shares of American Express,  a 22.1% stake that makes it the third-largest holding in the entire Berkshire portfolio at 14.7%. Only Apple at 18.5% is a larger bet. Valued at a market cap of $203 billion, American Express (AXP) stock is also part of the Dow Jones 30 index. Down 23% from its 52-week high, AXP stock currently offers you a dividen ...