I am playing one of my own scenarios again, Blood & Steel II a.k.a. Juggernaut and I want this to share with you.
I am now at the start of turn #8 and it looks like this: The map covers the northern hemisphere from India to Hawaii with playable civs everywhere (the US, Mexico, the British Empire, the German Empire, my brave New Romans and the Soviets; in between is the minor German allies civ). The map is stackable with the exception of mountain ranges - which is commonly believed to make the AI less aggressive.
And now, at the start of turn #8, my civ, is at war with the minor German allies civ, the German Empire & the Soviets. The German Empire is at war with me & the British Empire & the Soviets. The British Empire is at war with the United States, the German Empire & its minor allies. The United States is at war with the British & the Mexicans.
If that were not enough, all civs - even the German minor allies (i.e. the filler civ) is at war and conducts attacks whereever it finds anyone. The Mexicans advance into Texas & New Mexico while the US Navy raids the coasts further south. Naval battles and engagements take place in the Med, off the Portuguese coast & the Guld of Mexico.
So much for the bugger AI, eh?