LOS ANGELES, June 1 : The United States head into the World Cup facing perhaps higher stakes than any other team, with a deep run likely to accelerate the sport's growth in the country and an early exit from a favourable group threatening to stall years of progress.  Put simply, it may be the most important World Cup in U.S. soccer history. As co-hosts, the Americans were spared the grind of qualifying, leaving questions over the readiness of Mauricio Pochettino's squad heading into the