That's good to hear! Congratulations. As others have said on here, think of whatever it is that makes you stand out/more qualified than the competition. As you no doubt know, U.S. employers are the same when it comes to employing foreigners--those would-be employees have to prove they have skills/abilities beyond what the native-born applicants do.
In some ways, you have an advantage with a phone interview: you don't need to worry about wearing a suit, or having sweaty palms, or being distracted by the interviewer's combover hairstyle/overwhelming perfume/remnants of lunch in between his or her teeth. On the other, it somewhat limits you in breaking the ice; since you can't see the person you're talking to, you can't pick up on facial expressions that might key you in to what he or she finds positive or negative, and, worse yet, you're walking a tightwire if you try to lighten things up with any kind of funny remarks, as you can't tell right off whether the interviewer is somber and all-business, or laidback and as annoyed with interviewing as applicants are about being interviewed.
I have a quick, ironic story to tell you about phone interviews: Eight or so years ago, I replied to an ad in an "insider's" media/publications jobhunters magazine that came out twice a month in the D.C. area. The ad was from National Public Radio (NPR--for Brits unfamiliar with it, NPR's similar to the BBC in that it doesn't run commercials, has "highbrow" talk shows, etc.--it runs more or less on donations from the public). Anyway, the ad was for someone with an English or, preferably, journalism degree (which I had), who was familiar with and/or had worked at a radio station (which I had) to write for a weekly comedy show in which the "celebrity" of the week would be asked questions about current events, given humorous options for answers, etc. They wanted someone with a good sense of humor, which, obviously, is a very subjective assessment. Anyway, I sent them my "serious" resume with a witty cover letter, and thought nothing more about it. I'm going to quickly skip over this part--my then boyfriend (and childhood friend) died in a car accident, and after returning home from the funeral, literally 10 minutes after I walked in the door, my phone rang, and a man said he was calling from NPR's Massachusetts office in response to my application for a job they'd advertised. I was in a daze that day anyway, and it took me a minute to realize what he was talkng about--it had been at least three months since I'd responded to the ad. So I was really caught off guard, to say the least. I asked if I could call him back, but he said they were in a time crunch, had narrowed it down to three candidates, and if the phone interview went well, wanted to conduct a face-to-face interview in the next few days--they couldn't take callbacks, because they'd gone through several hundred resumes to weed them down to three, and were time-constricted. I told him that I'd just returned from a funeral, and to bear with me (and I could just imagine him sitting in his office thinking: "Yeah--just got back from a funeral. Now THAT'S a new one."). Anyway, he said he was impressed with my qualifications, my cover letter was very funny, etc., and I gained enough presence of mind to ask him exactly what the job entailed. He repeated the requirements,and he said that whoever was selected had to be prepared to move to Chicago on very short notice. I had assumed, since the job was advertised in a D.C. publication ,that the job was IN D.C., as the ad didn't indicate otherwise. So it made it very easy to say that he could narrow it down to two candidates, because I wasn't going to move to Chicago. Anyway, given all the circumstances, it was incredibly awkward, for both of us. If it hadn't been for the job location, I'd probably be kicking myself to this day for not going for it (not that I have anything against Chicago--I've always heard how cool it is, but then wasn't the time)--but I still think he would have weeded me out during the phone interview because being funny was the last thing on my mind, and that was an interview that absolutely called for being quickwitted.
Anyway, good luck, keep us posted, break a leg, may the force be with you, and any other cliche I may have left out.
Suzanne