u/Br0nn47

(Forgive if its already obvious, haven't played the CK3 version)

There are theories that IRL Greek Fire was an early form of Napalm, the latter is quite famous (or infamously) associated with America since Vietnam.

And even without Napalm directly, flammable liquids could maybe be created from the oil deposits around the Americas.

Could be a powerful expensive Regional MaA in places with oil, a Cultural MaA for advanced peoples or scavengers who recreated or uncovered knowledge to make something like Greek Fire, or Religious MaA for guys like Soiltappers.