Just imagine Mike Giles’s surprise when, after the US scored the dramatic game-winning goal against Ghana in the World Cup Monday, he looked up at the giant screen TV in his living room and saw his 18-year-old step-son staring - screaming, actually - back at him. ESPN had just shown a slow-motion replay of John Brooks’s header into the net when it cut to an ecstatic, frizzy-haired fan smeared in red, white and blue face paint. “I was with my daughter and my brother-in-law and we were all watching, and there was Jake, full-screen and full-face, on the TV,” said Giles, the chief technology officer of Boston-based Sun Gage Financial. “Then the neighbors came over because they were watching, too.” (Guess what, a lot of people were watching: The game on ESPN drew a 7.0 rating, which represents about seven million households.) A recent graduate of Amherst High School in western Mass., Jacob Lopez is a big soccer fan who saved money working at a bowling alley in Northampton to pay his way to the World Cup in Brazil. (The airfare alone was $1,500.) And he’s there alone. “He’s fascinated by world capitals and culture, and once wrote a rap song with all the capitals in it,” said Giles. “We’re a little nervous about him being there by himself, especially when he goes more than a day without touching base. But then he checks in and he’s having a great time.” Clearly.