Is there a lethal poison that can be made from north American plants?

there are some strongly poisonous plants in NA.

not sure about fast acting neurotoxins.

But there is hemlock, tobacco, oleander, rhubarb, daphne, rhododendrons, yew, mistletoe, nightshade.

Probably some I can't think of just now.

This might help.

http://aggie-horticulture.tamu.edu/lawn_garden/poi...

I'm not sure if you want to be hunting using poisons, since there will be poison present in the flesh of the animal if you use this method, so you will be consuming small amounts of poison. It won't necessarily kill you, but if you use an alkaloid-containing plant such as Datura, Nightshade, Hemlock, Tobacco, foxglove etc, then small amounts of the poison from these plants are known to cause violent and horrific hallucinations. I'd recommend using something other a poison from a plant from the family Solanaceae, aka the nightshade family. They aren't pleasant by any means. They will often cause a long, drawn-out and unpleasant death.

Although some plant-derived toxins are fine to use. The one i'd recommend using is Strychnine, which is used as a fast-acting neurotoxin for putting down sick animals in veterinary medicine. However, it's hard to find the plants containing Strychnine in North America, so that's out of the picture. You could try Aconite.

Nightshade (belladona) is probably the most commonly available. Purple star-shaped flowers with yellow centers, grows like a weed most everywhere.

apple seeds contain cyanide. (though you'd need a lot of them)

There's also foxglove.

I don't know how they'd work on an arrow or dart.