People who find this website are quite often looking for info on poison sumac, even more than for poison ivy.
But as you can see from the two map segments, there is MUCH MUCH more poison in the USA than poison sumac.
Poison sumac ONLY grows where it is very wet, often with roots in the water, which kills most trees.
Mind you, iNaturalist is not an absolute guide to where these plants exist: it is only a guide to where people have reported it.
But as the maps indicate, you will poison ivy almost everywhere: along every road, back yard, forest path, lake and stream side, and edge of fields. And where it grows there is usually vast amounts of it.
Whereas there are places where you might find only a single or a few poison sumac trees.
And of course, you can also find poison ivy growing around the poison sumac trees because it will tolerate those wet areas along with dry areas.
The other thing about this bean plant is that is is growing next to some big wooden parking lot rails which is where poison ivy grows so often… but in this case it was guarding the public from green beans!
