Last month, Rooney completed a transfer to DC United after just one year back at Goodison Park, where he scored 10 goals in 31 appearances in the Premier League.
Rooney has suggested that he would have been happy to remain on Merseyside, but the stance of the club gave him a decision to make regarding his career.
The 32-year-old told ESPN: "Obviously at Manchester United, that wasn't happening (playing) as much as I would have liked, and I quite easily could have stayed there with two years left on my contract and picked up the wages and been happy with that, and that's it.
"I wanted to play, went back to Everton and had a year there, then as I've said before, Everton made it clear towards the end of the season that they'd be happy for me to leave.
"For whatever reason, I still don't know. I felt I was doing OK, I was top goal scorer playing most of the season from midfield, but that's football. And that gave me a decision to make, and I made this decision."
Rooney is expected to make his DC United debut against Vancouver Whitecaps this weekend.