This mod removes Spirit Medicine tech requirement for native american archers recruitment, effectively re-enabling them in Grand Campaign. As simple as that.

To install the patch put native_american_archer_recruitment_fix.pack file into your game's data directory and create a user.empire_script.txt file in C:\Users\[User Name]\AppData\Roaming\The Creative Assembly\Empire\scripts and add the following line to it:
mod native_american_archer_recruitment_fix.pack;
The mod changes unit_required_technology_junctions and may cause conflicts with other mods if they change the same table.

Download here.