The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.NEW YORK ( Trefis ) -- American Express ( AXP) will report third-quarter earnings Wednesday. We expect the company to maintain its solid performance of recent quarters. Backed by positive U.S. retail sales data and American Express' own expansion efforts, revenue is likely to increase year over year. However, earnings may be affected by a tightening interest yield spread. The company's competitors include Visa ( V) and MasterCard ( MA). See our complete analysis of American Express stock here.