Myanmar struck first blood with a nifty shot from Yan Naing Oo nine minutes into the match. However, USA's answer came in the form of a crafty goal in the 17th minute off the boot of Maki Tall.
USA strode out to a 2-1 lead shortly after halftime through a goal via their captain Emerson Hyndman.
Nonetheless, Myanmar were positive, disciplined and kept the pressure on their more highly fancied rivals.
Aided by the hearty chants of "Myanmar, Myanmar" which circulated the stadium, the underdogs produced a spirited display in front of 5816 fans.
Just shy of the 70th minute mark, the rain - which so diligently avoided Northland Events Centre for the majority of play - drizzled down, adding another challenging element.
Close to the 80th-minute mark, Myanmar upped the ante as the crowd reaction hit a peak.
The decibel level rose as Myanmar picked up the tempo of their attacking effort.
But it was too little, too late.
Speaking to press after the match, Myanmar coach Gerd Zeise said his team were "a little bit unlucky" with the loss.
"I didn't see a better performance from the Americans, they only had more experience. I told [the American bench] that they were too clever for us and we must learn."
With the the two sides having never played each other at any level, many punters predicted a big USA win.
USA coach Tab Ramos was satisfied with his team's performance after entering the game without a win in their last four Under-20 World Cup fixtures.
"Obviously we didn't play the way we wanted to play," he said.
"At the same time winning games at the World Cup is always very difficult. I think we found in front of us a very inspired team.
"They made us play ugly and it was difficult for us so I'm happy with the win."
Everyone loves an underdog and in the context of this match, the football fans of Whangarei walked away with a full belly of top-notch footy.
After spending last week in Whangarei, Ramos and his team were blown away by the support from local spectators.
"I was a coach in the last Under-20 World Cup and there was such little support - to see all the local people come out, it was amazing.
"It was a great atmosphere, it's a great learning experience for the players to play in front of the crowd and I know they were excited - it was truly an amazing event today."
USA will now travel to Auckland to face New Zealand, while Myanmar stay in Whangarei to play Ukraine, 1pm tomorrow, at Northland Events Centre.
