President Trump hopped aboard a shiny red American-made fire truck at the White House Monday, and posed an unintentionally hilarious question ... "Where's the fire?"

POTUS smilingly got behind the wheel -- much like a wide-eyed little kid -- outside the White House with VP Pence and Sean Spicer nearby. It was all part of an event to kick off the administration's "Made in America" week.

By the looks of it, the Prez loved playing fireman in his youth. As for his question?

Follow the smoke ... his critics might say.