The Hammers have won just threee of their opening nine games under manager Julen Lopetegui, but snatched three points from a United side which were crumbling under now sacked manager Erik ten Hag.
Kilman discussed the victory and how changes made by Lopetegui impacted the game in a positive way.
“It's been a tough start, but we showed a lot of resilience and a lot of character,” he told the club's website. “We’ve seen with the second half performance how we pushed on and we've got a great result against a top team.
“All the boys who came on have done a great job and changed the game for us and that's what we need, the whole squad to push us on. Sometimes the subs coming on get the job done and that's how it was on Sunday.
“Cree (Summerville) is so good on the ball. He had a great moment with his goal and he took it so we’re all grateful. It’s great for him, and great for the rest of the team.”
The defender highlighted resilience as a major factor in the victory and opened up about what a tough start it has been in a Premier League season where three teams are yet to win a game.
“We had to show way more resilience in the second half,” Kilman continued. “The manager’s message was we just had to make sure we improved on that performance in the first half and we did. We had some really good moments, pressed really high, gained the ball in good areas and it helped that the fans pushed us on really well.
“There are so many top teams in the Premier League so, whoever you play against, you know you're going to be up against tough, tough opposition. Obviously Manchester United are Manchester United, so it was just great to win.”
Kilman also mentioned the penalty decision given by referee David Coote which he did not initially award but VAR deemed there was sufficient contact on Danny Ings’ lower leg and recommended an on-field review.
“I looked at it back and I thought that was the right decision,” he confirmed. “Of course, that's the referee's job, and he had time to look at VAR, so I think he got it right.”