Joe Biden Fired Up Over USA's World Cup Win, 'God Love 'Em!'

Joe Biden was so pumped America was able to pull out the win in the World Cup on Tuesday -- he straight-up led an old-fashioned "U-S-A!" chant at a political event!!

POTUS was out in Michigan while the must-win game against Iran was going down in Qatar ... and after the 1-0 contest ended, he grabbed the mic to gloat to the room.

Audio issues missed the first part of his impromptu winner's speech -- but it all clicked on just in time to hear him egg on a pro-U.S. shout.

"That's a big game man!" Biden said as the "U-S-A!" chants rang out in the room. "When I spoke to the coach and the players, I said, 'You can do this!' and they said, 'Ahh' -- they did it!"

"God love 'em!"

Back home in D.C., meanwhile, those still at the White House made sure they were showing love to the USMNT ... posting a "Go Team USA!" sign out in the yard.

As for the on-the-pitch action ... U.S. had to win the game over Iran in order to advance out of the group stage -- and after Christian Pulisic scored a goal late in the first half, they held on long enough to do just that.

Up next is the Netherlands on Saturday -- and the U.S. is already being billed as a HUGE  underdog in the game.