There is nothing called an ICAO license. ICAO is an organisation which most of the countries are member of. To make it easy on you guys for example, if an invidual hold a Indian ATP license, his country is a member of ICAO, so his/her license will count toward ICAO, but there are countries out there that is not a member of ICAO such as Trinidad Tobago (maybe they are with ICAO now),so in this case if a pilot hold an ATP license from Trinida CAA, he or she will not be consider ICAO/ATP because his country is not a member or does not meet the standards. And yes FAA ATP is an ICAO license. Several counties have a scheme called frozen ATP with mean you take your ATP theoretical exam and fly certain amount of hours and after you achive the flight time your license will become a ATPL.
Many people think that FAA license is weak, but don't forgett that most of the pilots that fly for Qatar, Cathay, Emirates, king fisher are FAA ATP holders.
Good luck