The Williams sisters, and more recently, shock U.S. Open champion Sloane Stephens rewarded the tennis hopes of any red-blooded American patriots. Frankly Serena’s haul alone should keep a country sated for a few generations. But U.S. men lag well behind. Ignoring the small sparks produced by Frances Tiafoe over five sets against Roger Federer, it’s difficult to come up with promising American men, names who could possibly win something of note during the the Euro-dominated era of Roger Federer, Rafael Nadal, Novak Djokovic, and Andy Murray. Can you name any American men at all? The servebot John Isner and Sam Querrey (who had a fine season) have probably both peaked, without any serious hardware to show for it. The biggest tournaments in men’s tennis are the four Grand Slams; the…