R.J.
You need to check your first source. There are many nations & hundreds of tribes on these 2 continents alone. Symbolism changes depending on the nation & tribe. The 'Native American people' or idea of a songle culture instead of hundreds, is a white thing.
As far as other cultures... Yup.
Downward facing arrows symbolize prepping for attack (archers stand their arrows into the ground for rapid fire before a battle) in some cultures, and are used in some pictoral writing systems to mean different things (including baptism for some modern US religious groups), as well as some US military units.
In GENERAL, I think arrows are used often enough that you don't have to worry about an immediate reference being made (unless its broken or headless, which is a way used by many cultures to tally the death toll, and in ours to symbolize certain things about bombs).
BUT I would reeally be leery of saying "Downward facing arrows symbolize peace" unless you can reference exactly which tribe or nation follows that.