ahh.. In vanilla, things are different.
I think the expansionist civs in Vanilla are:
Iroquois (Religious)
England (Commercial)
Zulu (Militaristic)
Russia (Scientific)
America (Industrious)
Industrious is a great trait in vanilla, so america is better there... but the F15 is still a poor UU.
The Cossack isn't as good, and scientific civs aren't quite as good, so Russia isn't as good.
Iroquois has a great UU.
England is sort of the portugal of Vanilla, but still playable.
For Vanilla, I guess I'd go with Iroquois - MW rule.