The West Bromwich Albion star, who is expected to line up against the Three Lions in Wednesday's international friendly at Wembley, qualifies as a Scot through the nationality of his grandparents.
"As a kid growing up in Darlington, I was very close to my family and their Scottish roots," Morrison told The Sun. "My grandparents are both Scottish - that's one of the reasons why I decided to do what I did."
Morrison, who admits that he was amused by Crooks's uninformed comments, believes that he would have been given the opportunity to represent England had he not have already committed to their fierce rivals.
He added: "Looking back, I probably would have had a chance to play for England by now... Garth Crooks certainly thought so.
"Any publicity is good publicity. I had a good laugh at Garth's comments. But my opportunity to play for Scotland came a long time ago and I'm glad I took it.
"I have never regretted my decision and I'll have no mixed emotions at Wembley."
Morrison is one of six English-born players - along with Matt Gilks, Russell Martin, George Boyd, Liam Bridcutt and Jordan Rhodes - to be named in Gordon Strachan's 29-man squad for Wednesday's match.
Meanwhile, Shaun Maloney was born in Malaysia.