There are differences if you know what to look for. I've often collected walnuts from trees in England and thought they looked similar. I don't need to check if the leaves are pinnate - they always are. If I hadn't been forewarned, I might have got as far as cutting the manchineel fruit open before discarding it, thinking it was a related species.

Lack of range overlap makes misidentification by someone from outside the range more likely.