The Red Devils won their final game of last season at The Stadium of Light.
Sunderland fans cheered and taunted United with a City-style 'Poznan' celebration.
"If it had been in reverse and City had lost out, I think our fans would have cheered United," said O'Neill.
O'Neill's side visit Old Trafford after a midweek morale-boosting win over Reading.
And he said: "We can go there with confidence.
"The expectation from others would not be great but that doesn't matter.
"We have to go and compete and I think the players are genuinely looking forward to it."