Got to ask:

Which is better, Cossacks 1 or American Conquest?

*Edit added*
I guess I'm mainly interested in which one has a better single player random map experience.

You will have to give us a little bit more about what you're looking for and if you are asking which one is more fun then I must warn that it will produce a highly subjective answer.

Personally, I think you would be better off with American Conquest. I found them both to be a little boring at times but the historical setting for AC was what kept my interest longer.

I guess I'm mainly interested in which one has a better single player random map experience.

Dunno about the random map generation part, but AC was a bit more balanced and polished. IIRC, that is.