Racial tensions depend on where you go for instance Windhelm tends to seem like the only city where outsiders are greatly unwelcome and places like whiterun are very open minded since they see foreigners very often since its a trading hub, same can be said in many places throughout tamriel.
You're forgetting the fact that you're stopped when first entering Whiterun and told the city is closed because of the dragons, the Alik'r are kicked out, and no Khajiit caravans allowed in to Whiterun like any other city. Nords in general are suspicious of outsiders, but that's no more true of Windhelm than anywhere else.
Except the stormcloaks are really racist and want a nord only Skyrim.
Except they don't.
Exactly! Really though, I think if you try to see the stormcloaks from the perspective of an elf, and try to imagine if these things were happening in real life (like I explained in my last long post) you'd see that most elves would throw their hat in with the empire. It would just be the natural psychological reaction. Does that mean one side is better than the other? That's a different discussion.
It really depends. Some people in the provinces have always felt that the empire was imposing a foreign culture on them. There's a reason the provinces are all jumping ship the first opportunity they get, and it's not just the Dominion's influence. You can choose to play a pro-imperial elf, but it's hardly a given. The empire is the premier example of Men trying to impose their will on Mer and other races.