The foreign ATP fills the FAA requirement to hold a commercial certificate. You would have to have your CAA verify your license to the FAA. And pass a TSA background check. Other than that, you go through the same steps a FAA commercial pilot does. (I'm guessing you want a ME ATP.) Complete a week long ATP Certificate Training Program. Study for and pass the ATM knowledge test. Pass the ATP checkride. The types are more of a minefield. You would have to be able to show the instruction was given by a FAA CFI or under a FAA approved program. You would then take the FAA IR knowledge test. Then you apply for a FAA private certificate based on your EASA license. That would give you a FAA private with the type ratings on it. THEN you go through all the steps listed above for the stand alone FAA ATP. The type ratings will transfer over. The problem will be showing the instruction was given by a FAA CFI. Even if the instructor held the FAA CFI for EASA training I doubt they would have signed the training off with their FAA CFI.