In his World Cup debut, Matt Turner made a number of vital saves against Wales, before a late penalty from Gareth Bale spoiled the Americans' party.
The USA were lively from the outset, in contrast to their uncharacteristically quiet opposition, and were rewarded for their dominance after the half-hour mark - Christian Pulisic's fine pass finding Timothy Weah, who dinked the ball past Wayne Hennessey.
The Dragons looked revitalised after the break and Turner stood firm as they searched for an equaliser, pulling off a spectacular finger-tip save to deny Ben Davies' diving header.
Wales' relentless pressure eventually paid off, however.