He said: "We have to keep looking at players like Rice".
"I think it's easy to be vocal when you haven't walked in those shoes", the England boss said.
It comes after the defensive midfielder, who can also play in defence, switched global allegiance from the Republic of Ireland.
Declan Rice has received his first England call-up just weeks after making the agonising decision to represent the country of his birth rather than the Republic of Ireland.
Like Rice, Everton defender Keane had a choice between England and Ireland with his father having left the Republic as a nine-year-old to start a new life across the Irish Sea.
"It's increasingly the case, if you look at our under 16s over 50 percent of them have dual nationality and some could play for more than two countries", he said.
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Such attributes led the Three Lions boss and former Football Association technical director Dan Ashworth to visit Rice before last summer's World Cup, when they made it clear they saw an worldwide future for him.
Rice's impressive form for West Ham in the Premier League this season has now earned him a place in Gareth Southgate's squad for the first time.
Preston-born former Ireland worldwide Kevin Kilbane has been outspoken about Rice's switch and said it "makes a mockery" of global football. His form has been excellent.
The squad also include Borussia Dortmund's Jadon Sancho and Burnley goalkeeper Tom Heaton who has been recalled after recovering from injury and regaining his place in the Clarets team. We like what we've seen in terms of his personality, his character and his leadership qualities.
England host the Czech Republic on 22 March and are away in Montenegro on 25 March. What I like about our squad is that a lot of players have the mentality that they want to be amongst the best players in the world. "So how far a player can go is entirely up to them".
The Three Lions face Czech Republic and Montenegro later this month as they look to build on promising performances at the World Cup and in the Nations League.
"But, we're pleased with what Jordan's done and we've got to help him through what was hopefully a blip at the weekend".