England are among the favourites for the tournament in Canada, Mexico and the United States after a string of near-misses at recent European Championships and World Cups.Henderson, speaking at England's Kansas City base, tipped fellow midfielder Bellingham, 22, to have a "big impact" over the next few weeks.The former Liverpool star said Real Madrid's Bellingham had made huge progress since his international debut as a 17-year-old in 2020."How much he's grown as a player and as a person since then is incredible, really," said Henderson."I had a good idea when I first saw him playing and training and the way he was. But what he's done so far at such a young age, I think everybody forgets how young he is, even me really sometimes."The Brentford player added: "I honestly couldn't speak highly enough of him. I know a lot gets written in the media. I find it hard to read sometimes, really, because I just know how big an influence he is on this team, how good a teammate he is off the field. "And what he gives us is just something really special, really. I think he really gives us the X factor in our team. "He's had big moments in his career. He's a big-game player. He's got experience in tournaments. So he's a huge, huge player for us in this tournament."England face a stiff test against Croatia in their Group L opener in Arlington, Texas, on Wednesday.Henderson admitted Croatia, who were runners-up at the 2018 World Cup in Russia and third in Qatar in 2022, would pose a tough test, picking out the threat of fellow veteran Luka Modric, who is 40."For me, he's probably the best I've played against in my career midfield-wise," he said. "I think his career speaks for itself. "I think he's a top world-class player, so hard to play against... I'm a big, big fan of his and hopefully he doesn't perform as well as we know he can against us."England's other opponents in Group L are Ghana and Panama.