I wanted to see if I could get a 4x100 relay estimate just by adding up the top 4 individual 100 free times for each country this year.
Men's times
AUS 3:11.88
FRA 3:12.41
USA 3:12.75
RUS 3:13.2
BRA 3:13.89
CHN 3:14.56
GER 3:14.73
JPN 3:15.2
BEL 3:15.45
GBR 3:15.52
Yep, those are a little slow, which is to be expected since most of those individual swims were not tapered, plus the differences between relays and individual events. It is interesting that there's only about 3.6 seconds difference between Australia and Great Britain.
Then there's the women's race...
AUS 3:30.98
USA 3:34.11
CAN 3:35.81
NED 3:35.84
CHN 3:37.24
FRA 3:37.27
JPN 3:37.61
ITA 3:37.68
BRA 3:38.62
RUS 3:38.64
A little over 3.1 seconds just between Australia and USA.