Sammie Smodzics had Ipswich before Kevin de Bruyne and a hat-trick from Erling Haaland saw City home.
"“We got off to a fantastic start, scored a great goal on the transition, probably the exact goal that we wanted to score today and we knew that we could score with their line being high and Sammie and Omari making runs behind, and he finishes it off well,” McKenna said.
“We got off to a great start and then the game was lost in a five-minute spell where there are some big lessons for us to learn, and I’m sure we’ll do that.
“The first goal is a penalty where it’s not a very dangerous situation. A one-v-one, but you know you’re going to have to face them at this level, but being disciplined to not give the penalty is really important.
“A 1-0 lead if we had have managed to hold onto it for 10-15 minutes, I think the base was there for us to have a really competitive game. I think everyone was comfortable with the plan we came in with and how we executed it in the few minutes.
“But 1-0 goes to 2-0 in the space of a matter of seconds, more so than minutes, and the feel of the game changes completely.
“And what I think’s positive and what was important from 3-1 was that we managed to get back hold of the game. We managed to show resilience, the team stayed together and we went from whatever it was, the 16th minute to the 88th minute without conceding.
“Of course, they had chances in the first half, but in the second we defended well as a team and didn’t give away too many opportunities.
“I think we had, in my eyes, a clear penalty (when Leif Davis was fouled not long before the break) and we should have gone in at 3-2.
“I know City could have had other goals but we should have gone in 3-2, it’s a really hard one to understand how it wasn’t given, especially with the intervention on the first goal, and we could have gone at 3-2.
“There are positives to take. There are, of course, some big, big lessons that you get from facing a team at this level and that’s normal for us to go through that with where the team and where the individuals are at. But again, I think it’ll be a positive experience in the season.”
Asked if he thinks they have enough to stay up, McKenna said: “I am. That’s not to say we were in any way dominant or we didn’t manage to make the game competitive enough today. But I’ve seen enough in moments.
“Last week, we made a really competitive game for 60 minutes against Liverpool and we showed the atmosphere, the intensity that we can play with at Portman Road and how difficult we can make it for teams coming there.
“Today, we didn’t have as much of the game, for sure, but we scored our first goal, we showed that we can come to the best team in the league away from home.
“And on a difficult day to play against City as well, let’s be honest. It’s their first home game, they’ve had a full training week, this is their first game here since they won the league, there’s great positivity around it, it was always going to be a difficult day to play them.
“But we showed we can come here, we can score on the transition and, of course, the spell of chances that they had and goals that they had is a period that we have to learn from. Similar to last week in some ways where Liverpool scored two goals in five minutes, so we have to improve on those moments.
“But on the other hand, we’ve shown in very small period of the game that we can play with the ball and play bravely and take the ball. It wasn’t enough today but it was maybe four or five moments in the game. We have to turn that into eight, nine, 10 and many more moments.
“I thought there were a lot of individual performances which were positive for us stepping up to the level and I think we’ll have taken a lot from the first two games.
“We’d like to be sitting here with points on the board but we know that the fixture list has meant that was going to be really difficult. We know we’re in an adaptation process, we’re coming with a group with so many who have climbed from League One in a very short space of time, we’re now trying to integrate new players into that. That’s not going to be an overnight process.
“But I think week by week, we’ll learn our lessons and I’m sure we’ll improve over the weeks and months to come.”