Townsend, 22, was a surprise starter for Roy Hodgson's side, but justified his inclusion with a man-of-the-match performance that saw him set up England's first before rifling home their third from distance in a vital 4-1 win at Wembley.
The result left England top of Group H with one round of fixtures remaining and knowing that victory against Poland on Tuesday will seal their qualification for the World Cup in Brazil next year.
"I'm so proud to have represented my country and to play well and score really is a dream come true," Townsend told Spurs' official website.
"I tried to play my normal game and everything went well. The most important thing was the win, it was a huge game.
"It hasn't really sunk in yet. All I'm thinking about is Poland on Tuesday and then it's back to Spurs and preparing for Villa.
"JD (Jermain Defoe) and Kyle (Walker) have been giving me a bit of stick (about not scoring), so it's nice to keep them quiet for a while!"
Reflecting on the moment he was told he would be starting against Montenegro, he said: "I found out lunchtime on the day of the game.
"The manager came to me a few times during the week and said he was undecided in that position, a few players were vying for it. I'm so grateful I got the chance and I'm pleased I was able to repay his faith in me.
"I didn't really think about it, about how big it was. I was excited to get my first start and was determined to make the most of it.
"It was only afterwards that I thought how big a game it was for England - if we hadn't won it we wouldn't have been in prime position to qualify
automatically for the World Cup and that would have been unbelievable."