Elves

Elves live in "the Americas", humans live elsewhere in the world. There was never a land bridge to the Americas, so the only humans ever in the Americas before Europe started colonizing were a few failed Viking colonies. Elves live until they're killed. Thousands of years "ago" the Elves had a huge war over their leadership, which decimated the Elves and laid waste to most of the Americas, and killed both/all of the people who wanted to lead. When it was all over, they deliberately rebuilt their society with values of individualism so strong that not only would they violently object to government, but also to individuals taking power on an informal basis- kind of uber-libertarian. They tend to be very polite, because if another takes offense there's nothing stopping them from killing you- although most of the time deaths actually only happen when somebody tries to take power over another Elf or Elves. The children are also brought up this way, only forced to do anything when they're too young to take care of themselves, which probably wouldn't work so well if it wasn't for their lifespan. After the war, they "rebuilt" the Americas, making them into mostly massive forests of giant trees (which they build most of their buildings in). The Elves have integrated magic into nearly every facet of their lives, so there isn't a lot of need to work together to do anything. Antisocial when compared to humans? Differences between younger Elves and those raised before the War.
The humans are Europeans at the time of the Renaissance. The only difference in them is that there are a very few of them who do magic- everybody has the potential, but a number of factors combine to make it less prevalent. Magic is only taught at University, so only upper class, highly educated men have the knowledge to do more than maybe lighting a fire with it. Human magic is less advanced than Elvish magic due to its limited use and the lifespans of the humans- half their lives are spent just learning it! Since it's the Renaissance, they do the exploration thing and eventually colonize the Americas, neither knowing nor caring that they're already occupied. The Elves take quite a while to notice that they're there.
And then there's a clash of their cultures. When it comes down to fighting, the Elves have most of the advantages- magic, knowing the territory- but technically humans have more technology, and more people if they want to start a war, and they're used to teamwork- they can't even build houses without teamwork. Their cultures are completely incompatible.

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