This is definitely a new era in U.S. chess, when it's possible for an American fan to feel slightly disappointed that they split the match on the open side while winning in the women's event. But only a little disappointed, especially since the U.S. team was a clear underdog and a bit lucky to win the women's match.
In the open section there were some big ups and downs. On boards 1 and 2 the Russians were in excellent shape early on: Sergey Karjakin was clearly pressing against Fabiano Caruana, while Vladimir Kramnik had equalized without any problems against Hikaru Nakamura and was maybe even a tiny bit better. Any anxiety U.S. fans might have had about those games dissipated fairly quickly. Nakamura immediately hunkered down and drew easily, while Caruana got out of trouble before the time control and drew almost immediately afterwards.
That left two games: Ian Nepomniachtchi vs. Wesley So and Ray Robson vs. Alexander Grischuk. "Nepo" came into the round 7-0, but confidence and the white pieces notwithstanding So was a stronger player than any of his first seven opponents. So outplayed him nicely and was winning well before the handshakes made it official. As for Robson, he went for the insipid 5.Re1 Anti-Berlin, and obtained a position that couldn't possibly be lost. Unfortunately, as we all know, there is almost no such thing. For some reason Robson burned tons of time in a relatively simple middlegame, and once he got in time trouble he committed one of the most typical errors - repeatedly - in shoving up his pawns all over the board. All that did was wreck his position, creating both weak pawns and weak squares. Maybe he hadn't had time to realize that a draw would have been a great result, and thought he needed to press and maintain some tension. Or maybe it was just a lack of international experience showing. He's a great player but very young, and hasn't yet had the chance to play in super-GM events yet. Whatever the story, the U.S. is still in great shape. They drew the match, remained ahead of the Russians, and lost only their first game of the entire tournament.
Note, however, that being ahead of the Russians doesn't mean they're in clear first. They do lead on tiebreaks at the moment, ahead of India (victors over England, 2.5-1.5 thanks to Sethuraman's victory over Short) and Ukraine (which beat Georgia 3-1, despite Jobava's miniature over Ponomariov). Ukraine and India play in round 9 tomorrow, while the U.S. will face Norway(!), which has cobbled together a great Olympiad despite their low-rated team (excepting Magnus Carlsen, obviously).
In the women's section China and the U.S. are tied for first, with China leading on tiebreaks going into their clash tomorrow. China easily dispensed with the overachieving Azerbaijan team, 3.5-.5, while the Americans squeaked past the Russians. Katerina Nemcova crushed Olga Girya on board 4 to give the U.S. an early lead, but Valentina Gunina equaled the scores by defeating Nazi Paikidze on board 2. Anna Zatonskih had some troubles with Natalia Pogonina before holding a draw, so that left only the board 1 clash between Alexandra Kosteniuk and Irina Krush. Krush's 10th move was a mistake, and she was seriously worse for a long time because of it. She held on though, and by the time control the position was equal. At this point Kosteniuk had to decide what to do. She had a couple of opportunities to close things down and get out with a straightforward draw, or she could push for more. Perhaps if she hadn't been so much better for so long earlier in the game she would have taken the objective view and assured herself and her team of a drawn match, but she went for it. The result was an ending where only Krush had winning chances, and Kosteniuk kept making her situation worse. I'm not completely sure that Krush was winning on the penultimate move, but when Kosteniuk blundered a piece to a nice but simple two-move tactic the game was immediately over.