The 26-year-old missed out on the Three Lions' Euro 2012 campaign after breaking his jaw in a warm-up friendly international against Belgium.
"Now I'm back fit but there is real competition and I think myself not making the Euros has made it harder," Cahill is quoted as saying by Sky Sports News.
"I thought the lads did well in the Euros so for me not being able to stamp authority in that tournament has made it another fight for me to get back involved and get the starting place.
"There is great competition and the lads who are picked want to keep hold of the shirt. It is going to be tough but it is a fight I've had since I've joined because we're blessed with some good players in England."
Cahill is currently with the England team preparing for their 2014 World Cup qualifier against Moldova away from home on Friday.