The 23-year-old surprised many with a series of outstanding displays last season, which attracted interest from a host of Premier League clubs this summer.
However, McCarthy insists he is happy at Reading, and hopes he can continue to be part of Roy Hodgson's England plans.
"To play for England would be a dream come true and to make my debut at Wembley would be incredible," McCarthy told the Daily Mail.
"I was over the moon to be called up last season, especially for the Ireland game, and then going to Brazil.
"Going to Brazil for the World Cup is a realistic target for me. There are not a huge number of keepers out there, and I believe if my performances are up there, then I have a chance."
A series of loan moves saw McCarthy turn out for the likes of Bath, Aldershot and Brentford in the past few years, moves he believes got him where he is today.
"The loan moves have been massive," he added.
"There is only so much you can learn in training and playing reserve games.
"When you're playing for points, it alters the decisions you make, so the earlier you get out on loan and experience that, the better."