Newcastle were comfortably bounced out of the competition by City 3-1.
With a Champions League clash against Barcelona on Tuesday, Howe admits his priority was always Europe, even ahead of the Premier League.
Howe said: "In terms of trying to achieve something totally memorable, yes. All energy and focus now go to Tuesday."
"My focus is really short-term, and it's trying to win the game that is in front of me, and that is winning the game against Barcelona in the Champions League.
"As much as it is easy to be negative in this moment, and I understand we have gone out of the FA Cup, we have the biggest game in the club's history coming up in no time at all. We have no time to dwell on this."
After thanking the fans at the final whistle, Howe also said: "The supporters were incredible. That second half, when it was very difficult for us, they were still behind us and cheering for us. That typifies the crowd here. I was saying that I was walking around.
"This is an amazing football club and full of incredible people. We are going to need every single person who enters the stadium on Tuesday to try to make the difference for us.
"That is really now our season - it's in the hands of the next two games in the Champions League."