The Portman Road club are impressing in the Premier League, especially after claiming a 2-2 draw against Aston Villa.
Now that the former Leeds man is no longer playing in the Championship, McKenna believes Lief is worthy of an England place.
“That’s obviously going to be for other people to judge and for Lee Carsley to judge at the moment,” he said.
“I think Leif’s strengths are clear to see. I thought today was probably his best performance.
“He wasn’t happy himself with his level last week, so I thought today was his best performance and I think he’s got fantastic attributes as an attacking left-back, who can cover distance down the line, deliver really good balls to forward players, both to feet and in crosses, and be a threat coming in at the back post.
“He’s got fantastic attributes, I think his defensive game is improving, it will improve over the course of the season, I think it already has improved over the six games with the lessons that he’s picked up in some of the early games.
“And I think he’s in a great place in his career. He’s 24, he’s playing his first year in the Premier League, he’s picking up experience every week in a team that support him well and if he keeps working then I’m sure he’ll show his quality over the course of the season.”