Are your licenses FAA, and have you ever trained in the US. If so, it won't be a problem. I have instructed a couple of foreign pilots. One guy from Norway who did all of his training in the US, wasn't a citizen, had a green card and all of his certificates were FAA. If that is your situation, you shouldn't have any problems getting your ATP. If you have foreign licenses, and are not a citizen, than you need to contact the TSA, and get a letter from the country where you got your licenses proving that they are legit, and you will also need a letter from the FAA saying that they understand that your foreign licenses are legit. Honestly the best thing to do is call the local Flight Standards District Office and tell them your situation. You can find their phone numbers for your location at www.faa.gov I believe.