relays come down to a lot more than just head to heads.
see the womens 200M free relay for evidence of that.
They were always going to finish in the top 3 - no doubt in the world. Look at the swimmers - they didn't have ones near the top, but their worst swimmers were better than the majority of the worst swimmers from other countries.
That doesn't apply with this relay, with the US worst swimmers better than most countries best swimmers.