Xenophobia and racism are not related. Xenophobia is about foreigners regardless of race, and racism is about race regardless of nationality. The two get mixed in the head of people from the USA because a lot of guys claim they’re Irish or Italian without ever having set foot in any of those countries. If you dislike your [insert ethnicity] neighbour who was born and grew up in the same place as you did, you’re being racist. If you dislike your [insert nationality] neighbour who’s the same ethnicity as you, you’re being xenophobic.
-phobia means an irrational intolerance, for a lot of things we express intolerance by showing fear, but to others we show aggressiveness. It depends more on the person than the subject matter, some homophobics are actually afraid of gays, thinking they’ll corrupt the children or whatever stupid fearmongering propaganda they’re up to these days, meanwhile some arachnofobics will kill every spider they see. And their line of thought is often quite similar, e.g. I don’t hate [gays/spiders], I just don’t want to see them.