IRVINE, Calif. — Nearly a decade and a half ago, two 13-year-old boys stood on the eighth level of a stairwell at a California hotel tossing wads of chewed gum, trying to get it to stick to the fronds of a palm tree below.The kids — one from Texas, the other from Pennsylvania — had just met on the bus taking them to a U.S. under-14 training camp, a random happenstance of choosing a seat one row in front of the other. Christian Pulisic and Weston McKennie couldn’t have imagined that 14 years later, they would walk together onto the field of a stadium just a few miles away from that hotel, leading their country into a home World Cup.The U.S. men’s national team will open its tournament on Friday evening at SoFi Stadium in Inglewood. It will carry with it a pressure and expectation foreign to most U.S. men’s teams. This group has been called a golden generation, one expected to deliver a deep run in the World Cup even despite the program’s history of only ever having won one knockout game since 1990. It is a once-in-a-lifetime opportunity to play in front of home crowds and galvanize an entire nation behind the sport.The U.S. team has accepted those expectations without fear, in part because the fibers that run through the group began forming more than a decade ago, when they were just kids dreaming together that they might get a chance to do exactly this.“It helps, it just gives you that extra level of comfort,” Pulisic said on Thursday. “You want to fight for guys like that. I played with some of these guys for so long, you don’t want to let them down. You want to give them everything, you want to have their back always. And I think that pushes you through in tough times.”In order to understand this U.S. men’s national team, you have to understand that it isn’t just a group put together over the last two years by Mauricio Pochettino or even over the last nine since the failure to reach the 2018 World Cup in Russia. It is a group in which many of the core players have grown up together, from proms and pro debuts to marriages, kids, trophies and record transfers. They have experienced firsts together — national team debuts and World Cups — and gone through lows together — bad loans at clubs, Copa América failure and coach firings.