Norwood picked up 57 caps for his country but decided a year ago to concentrate on his club career as he prepared for the challenge of the Premier League with the Blades.
The 29-year-old had been let go by two previous clubs – Fulham and Brighton – with which he had won promotion from the Championship and felt that he should concentrate on proving himself with Chris Wilder’s side in the top flight.
The decision didn’t go down well across the Irish Sea, but despite Northern Ireland standing one game away from qualifying for their second successive Euros after a penalty shoot-out win over Bosnia-Herzegovina on Thursday, Norwood says he has no intention of reversing his decision.
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"I always found that the first two or three games after an international break I was struggling. You get to a point where something has to give," he told BBC Radio 5Live.
"I noticed a difference in my performance before I went away compared to my performance when I came back.
"It was affecting my performances for whatever club I was playing for and I didn't think I was giving myself the best opportunity to perform for my club.
"It's probably not good for people to hear, but at the end of the day your club career comes first."
"I didn't want to miss any Premier League football or be unavailable by picking up niggles or being tired, then being left out of the team as a consequence of that," he added.
"I get a lot of stick and people question it, but people don't know what goes on every single day and what your body is going through.
"Mentally as well, we are in a privileged position as footballers but sometimes you do need a break."
That said, Norwood is obviously delighted to see Northern Ireland on the cusp of qualifying, with only Slovakia now standing in their way next month.
"The game against Slovakia, in Belfast, I think it is ideal for them," he said.
"In a one-game scenario, I'd fancy Northern Ireland to beat pretty much anyone at Windsor Park and I do believe that they will qualify."