I remembered watching Last of the Mohicans when I was in Middle School, and the ferocity of the Native warriors portrayed in the movie helped me come up with a new Unique Unit, if we ever have a new DLC that takes place in North America. Although the movie takes place in the time of AoE3, there were also Native American factions in the Vinlandsaga campaign called Skraelings (technically Algonquins).
Here is the proposed UU below:
Mohawk Maceman/Tomahawk Warrior
Algonquin unique infantry unit that instantly slaughters any foot unit in one blow once the HP of the unit they are engaging is reduced to half of its HP.
Cost: 40 food, 20 gold
HP: 80, 90 (Elite)
Base Attack: 7, 9 (Elite)
Base Armor (Melee/Pierce): 1/1
Other upgrades: Warchiefs (UT): Tomahawk warriors deal double blows per hit (The second hit deals 50% less damage than the first).