Anything from 1500-1860 opens up a whole lot of warefare outside of the Americas.The Big ones include 30 Years War and the Napoleonic Era.The major players in those campaigns may well be inserted into the game for the overflow effect into the Americas.
However Wars of Independence and Revolution in North, Central and South America seem more possible.
As for expansion packs, the door is open for the whole thought of Imperialism that swept Europe as Africa and Asia were being colonialized from 1870-1900.
Somehow I get the feeling that Native Amerians will enter the picture, if not out right than via MOD packs.
So with all that said, it looks like:
Britian, France, Spain, Germany, Netherlands, Russia and 2 others are in.
Who are the two others?...........my guess is Sweden and Portugal.
The only other "European" to set up colonies "in the Americas" was Denmark.
Perhaps Sweden/Norway/Denmark will be represented as one called The Kalmar Union.
If that is so, Portugal is historic in South America.....but maybe Spain and Portugal are also one position.
That makes room for the other naval power of the 1500-1600's Venice.(or Italian States)
"The Greatest pleasure is to vanquish your enemies and chase them before you,to rob them of their wealth and see those dear to them bathed in tears,to ride their horses and clasp to your bosom their wives and daughters"...
Ghengis Khan