The sharp winger fittingly bagged on his 300th league game, striking home the Eagles' opener just minutes after kick-off.
He caught up with Sky Sports post-match to reflect on an incredible 90 minutes, saying: "Moments like that [scoring], when I do retire, I’ll obviously cherish. It means nothing if you lose on one of those milestones but to cap it with a goal and a very impressive victory at Old Trafford is one I’ll remember for a very long time.
"We know we’ve got quality in the squad. We showed it at times last season. This season we have one or two young players, as you saw when Ebs [Eberechi Eze] came on at the end, we added that.
"We’re fully confident, we knew it was United’s first game and maybe we could catch them cold. We did that in the first five minutes. Once we get ahead we know we’re a very well-drilled team and we knew we had enough in the dressing room to see out the result today and we more than did that."
Townsend dismissed the notion that the Eagles were sharper due to United having not played a Premier League minute this campaign, but he did concede that the host's delayed start may have provided a psychological advantage.
He said: "Mentally we knew we had an advantage. Whether that meant something or it was just in our minds, we knew if we started fast we might catch them cold and we certainly did that. It was just about seeing out the game plan."
But the experienced No.10 also made it clear that he and his teammates are staying grounded after such a performance, commenting:
"Last season showed us we can’t get carried away. We’ve had a good start, but it doesn’t get easier next week - Everton, who are flying high. We know we need to keep our heads in the game, to take it one game at a time like the old cliche goes.
"We know we’ve got it in the dressing room to have a good season, like we did last season. We fell away last season and hopefully we can learn from our mistakes this season."