The US lost by 2.375 and most of that was two misses from from an injured athlete who usually hit those events and wouldn't necessarily have been doing both/either anyway. Had Chellsie been healthy, she'd likely have done floor instead of Alicia which removes half of the loss straight away. She was the better of the two in 08, and Alicia struggled to get out of the low 15s internationally in that code. Beam is harder to call. I think they'd probably have just put the top 3 up from prelims, which could've been any of the four really.
It's true the US weren't going to be able to match China on bars whatever happened. But they didn't need to. China were about a point ahead after two events, then Cheng Fei fell on beam. As the US stepped up, there was nothing in it.
It also tends to get missed that Cheng Fei wasn't consistent with her full difficulty on floor, and that this could've been significant if things had worked out slightly differently. She was able to water down in TFs, safe in the knowledge that staying on her feet would be enough. Had there only been a few tenths in it, that wouldn't have happened. We all saw how that went in the EF, when a medal was on the line.
Shawn would also not have watered down her tumbling in TFs if it were going to come down to tenths, but unlike Cheng Fei she actually successfully competed her full difficulty in Beijing when medals were riding on it. There is evidence that Shawn could do it, but not that Cheng Fei could. Once Alicia had competed, the title was decided, and the subsequent floor performances wouldn't have been the same if it had still been up for grabs.
None of which is to say the US would definitely have won. And they couldn't have beaten a lights out China either. But had the Americans gone in healthy, they could've pipped the Chinese performance that day.
