How do we know that the cup, as opposed to those who are competing for it, are American? And if it were made somewhere else, would the players really care? The tournament is about two things (or three): money (& prestige), and for Levon Aronian, the possibility on a miracle scenario of gaining enough points to leapfrog Ding Liren to qualify for the Candidates (assuming Sergey Karjakin's appeal is denied).
To that end, Aronian got off to a good start, defeating Ray Robson in game 1 of their match. (Which was rated, according to the 2700chess.com site.) Robson offered a pawn in a known line of the Reti that reaches a kind of reversed Benoni. He initially enjoyed sufficient compensation, but it evaporated. Aronian reached a winning heavy piece ending that turned into a winning rook ending, and he converted his advantage smoothly.
Lenier Dominguez and Sam Shankland split the point in the first game of their match, a lively theoretical battle that demonstrated that Shankland had done his homework. I wouldn't be even slightly surprised to learn that the whole game was in both players' computers before the game; if not, it was impressive play at the board.
The match between Wesley So and Sam Sevian started with an upset. So, with the white pieces, enjoyed the advantage in a sharp position with the kings castled on opposite flanks. Sevian outplayed his higher-rated opponent and achieved a winning advantage, but a big mistake on move 31 gave So the chance to save the game. His first two moves were correct, but his third move was a blunder that lost almost immediately. Instead, he could have saved the game with a beautiful and precise tactical sequence, but - maybe due to time trouble? - he failed to find it.
Finally, Fabiano Caruana and Jeffery Xiong fought it out in a Petroff that first saw Caruana and then Xiong have great winning chances before the game finished in a draw.
These are mini-matches, so game 2 will see the same players fight it out tomorrow/today/Thursday, with colors reversed. Today's games are here, with my comments to the first three.