Then I think you're not applying the proper definition of xenophobia. Xenophobia is more along the lines of the equivalent of racism towards foreigners. In order for the United States to be a xenophobic nation, you have to look more at it's culture, not the policy of the United States Federal government.
Looking at the culture of the United States, most of the anger towards foreigners in the United States is directed more towards those who enter the country illegally. They're the ones who drive down labor wages and make the labor market far more competitive due to their unfair advantages. As for foreigners who enter legally and work hard for the benefits of citizenship, they're pretty well tolerated. And American culture has embraced them overall. We have absorbed aspects like Cinco de Mayo, ethnic neighborhoods like Chinatown, Little Italy, music, etc. into American culture. We overall embrace other religions, particularly Judaism. And hell, the Statue of Liberty has the New Colossus poem engraved on it's pedestal. Now let's compare this to say France, which pretty much expects you to completely drop your ethnic identity in public society.
Looking at the policy of the United States government towards foreigners, again, not really xenophobic. Foreigners who enter legally are entitled to the same protections of the law as citizens and those who become citizens are entitled to the same benefits that you and I get. Now compare that to say Japan, in which anyone who isn't ethnically Japanese, even though they live in Japan, were born in Japan, and can speak only Japanese can't even hold public office. And this law was affirmed by their legal system.
Or hell, look at the politics of the United States. The United States would never have parties like the Freedom Parties of Austria and the Netherlands or Greece's Golden Dawn or France's National Front ever become an influence in the political sphere.
Now you can criticize the realist foreign policy of the United States. But realism is based more on the grounds of "might makes right" and the general best interests of the nation as opposed to xenophobia.