Interesting question! But oh my goodness, I have to start by saying this is a small-talk topic for Bay Area Natives. We talk race politics like other people talk about the weather. I think that's different elsewhere, no?
I think American (second generation and beyond, first generation being the people who immigrate) - American young people are more comfortable in greater numbers crossing the ethnic divide. I work with one girl of Vietnamese heritage who is out looking for a good Mexican boyfriend. She says she wants Mexican Christmas. Her sister-in-law, who also works with us, however, is more caught in the middle. She tends to talk about salad as mysterious and exotic while being totally down with sushi - because that's a natural, Asian food.
I do think young people who have grown up in mixed communities are in fact multicultural. It's not just "cultural exchange" - picking up stuff here and there from other cultures - they really live these bits and pieces. No matter what their parents, or others more singularly culturally attached, think. I'm not young, but I did grow up in the Bay Area. I think my life has been somewhat a prototype for the *brave new world.* Black people ask me if I'm black. Filipino people ask me if I'm pinoy. My mum's neighbor tells me I need to make pilgrimage back to the Motherland (China) for a good husband. And last but not least, I'm as WASP as a non-white, non-anglo, non-protestant can be: I subsist on gin and saltines, after all. It goes like that.
What I consider myself is mixed, heritage wise. I'm Chinese, German, & Scotts, with an overlay of British Colonial mannerism. My people have been in the new world for almost 175 years. I suspect the German "mind set" is pretty dominant: I'll talk lovey to my dog, but not to you. Hahaha!
I will say it's a little funny, because personality wise - I'm a person rooted in place. I know fully where I'm from, in excruciating detail. Anyways, I want to say something: we've gone from the Great American Melting Pot to Diversity as an ideal (promoted heavily by my own township) and I feel it's the worst thing ever to happen. It's fracturing. I don't like it and think it was a bad, bad idea.
Last but not least we're on a new wave of immigration. New, later layers of immigrants. What they think is Irish or French or Asian or Latino is not what the folks already here think of as Irish, etc. etc. It's a double cultural-clash.
I could go on babbling, but I'll stop now. I mentioned it was like talking about the weather, right?