John Isner, Sloane Stephens give U.S. winning start at Hopman Cup

In other first-round matches, Yvonne Meusburger beat seventh-seeded Mona Barthel 6-4, 6-3 and fifth-seeded Jamie Hampton beat wild-card entry Tamira Paszek

John Isner and Sloane Stephens virtually ended Spain's chances in international mixed team competition :: Will Russell/Getty Images

In other first-round matches, Yvonne Meusburger beat seventh-seeded Mona Barthel 6-4, 6-3 and fifth-seeded Jamie Hampton beat wild-card entry Tamira Paszek 1-6, 6-0, 6-3.