Why didn't France just invade and wipe out all those pidly little German states to the east. When you play as France, that seems the obvious move, right? So why did major nations like France, Spain, and GB basically maintain their Euro borders and focus primarily on expanding their overseas holdings? My guess is it has less to do with standing armries, more to do with the ability to quickly raise troops, and most especially the power of culture to make such invasions prohibitively expensive (the cost of garrisoning entire nations that will constantly be in rebellion for year after year). Except for France I guess, since they seem to roll over for whoever invades them.