18-year-old soccer phenom Christian Pulisic is "worth the hype" -- and gives the U.S. a real shot at winning a World Cup ... so says Alexi Lalas

Pulisic is killing it right now -- he's scored or assisted on 7 of the U.S. team's last 9 goals -- and he's been hailed as the future of American soccer. 

Lalas says the hype is real -- telling TMZ Sports, "Get on the train! Don't worry, you're not going to break him. We have high expectations. He is something pretty special."

Alexi is a legend himself -- he played for the U.S. national team from '91 to '98. He's now a soccer analyst for FS1 and just came back from watching Pulisic and Team USA play Mexico. 

"Even at 18-years-old he's someone to build this team around for the next 10 years," Lalas said ... "He's fun to watch."