Soccer nerd here, forgive me.
Abby is old, it is a known fact. She may not start all games, may not even play in all games. Her presence changes the way opponents play, sometimes you want to force that. At other times, her style doesn't fit well to go against today's defenses - so depending on the opponent, she may not be used. This is her last WC, everybody knows that. Some weren't sure she'd make the squad.
Also, we are in a generational transition with this team. There are a few older players like Abby and Rapino, and a lot of new faces even among the starters. They have had the past few years to sort out who of the next generation is good enough to make the squad and possibly start. They have also had that time to use friendly matches to work out chemistry - who works well together on the field. I don't know if this opening game was just jitters or if they are still figuring out chemistry. It doesn't look like they are a whole unit as yet.
The team overall looked asleep to start the game, though I credit AUS with coming out of the gate strong and hard, they pressed us and were dominating out of the gate. 10 min in, the US settled down and started playing better, playing their game a bit more rather than trying to react to what AUS was doing. We are one of the top teams in the world for a reason, we are f'n good. That said, we aren't always on top of our game. And, for those of you who couldn't stand the way we played, skip the rest of the games. Women's soccer may not be for you. That said, you have a choice to watch or not - don't watch and bitch. Watch and enjoy, or don't watch.