Musah, formerly of Arsenal, was capped at youth level by England before committing to the USA.
He told Valencia's website: "I didn't think that it would come around so quickly. I'm only 19 years old and I'm getting to play in a World Cup. I am very excited about it"
"Rather than being nervous, I am very happy to have this great opportunity to play in a World Cup. A lot of great players haven't been able to play in one. I'm happier than nervous.
"After a lot of effort, it's always nice to receive a reward that keeps you motivated. Every player wants a reward like playing in a Champions League final or a World Cup, It's a huge thing."
Musah also said: "I think we've got a chance to qualify and get out of the group stage and that would be great for me. I thnk we the ability to do that. My national team debut was against Wales and it also be my first game in a World Cup. It's a special game.
"The game against England it's going to be very exciting. Everybody that I know in England will be watching. Even those who don't normally watch football will be watching it. When there is a competition like the World Cup, everybody supports the team.
"It's going to be a special game, playing against players like (Bukayo) Saka who was my teammate at the Arsenal FC. We have to beat them, right?"