The best way to beat a team that's bunkered in is to maintain possession and force them to chase the ball. Those quick passes in and back out that probe the defense and force defenders to chase may make for boring TV, but it's physically demanding and will (as it did in this case) open up space in the second half as the defense fatigues.
The one takeaway I had from the Gold Cup was that the US looked light-years better than I've ever seen on first touches. In the past, you'd see the US (at all levels) give up possession or lose opportunities for good runs because the first touch (or the pass itself) was so poor that it led to dispossession or threw off timing. In this tournament, the US was, in every match, the more polished team in terms of passing and touches. That hasn't been the case in possibly forever.