Terrence Boyd has entered for the United States to start the second half. He's on for Landon Donovan, while DaMarcus Beasley has entered as well, for Jose Torres. The USMNT was playing without wingers in the first half, but Beasley is a wide player and isn't going to replace Torres like-for-like. This is almost certainly now a 4-4-2 for the United States.
Mexico has made some changes as well. Elias Hernandez has come into the game for Manuel Viniegra, while Rafael Marquez Lugo has come in for Pablo Barrera. Mexico is probably going to have less width, but they're going to look less solid deep in the center as well. These are almost certainly changes to exploit the fact that the United States isn't exactly packing the midfield. Angel Reyna wasn't exploiting the space between the midfield and defense in the first half, and the two subs should do a lot more of that.
Boyd got off to a great start with his new club Rapid Vienna to start this season, but his play has cooled off considerably. Even with the United States' lack of depth at striker, he'll need to perform in this game and going forward for his club to stay in the team for competitive matches.