It really transformed Europe too. Europe's basically a story of famine after famine until they got access to the potato. I don't know if any other technology has saved as many European lives as the potato

Pacific island cultures are a bit unique in their relationship to the New World though. Chickens which come from SE Asian jungles have been in South America since at least 1300 AD. And sweet potatoes were grown in Polynesia around 1000 AD.