I find the apparent belief that a UK 'Frozen ATPL' is a licence in its own right quite fascinating.. .. .It's not. The licence held is a CPL, with passes in the ATPL subjects. . .. .The licence that is held is what is recognised by other ICAO countries. It doesn't matter what other exams at whatever level you have. The question is "What licence do you currently hold?".. .. .Unless you hold the experience requirements for an FAA ATPL you will only be able to do the exam & test for a CPL. If you DO hold the experience requirements for an FAA ATPL why not get a the UK ATPL? The requirements are damn near the same. Perhaps not quite so under JARs WRT the multi crew requirement.. .. .A significant difference, though, is the FAA requirement to undertake a flight test for each licence issue. Unlike the UK (& Oz, for that matter) where an ATPL can be issued as soon as the experience requirement is met, in the USA you must sit a flight test for the ATPL for the class of a/c you wish to be licenced for eg Single Engine Land, Multi Engine Land, S/E Sea, M/E Sea.. .. .The upshot is that the typical fATPL in the UK will only be eligible for an FAA CPL (a VFR licence) requiring an exam + flight test.. .. .To get IFR privileges will require another exam + flight test.. .. .To get ATPL will require yet another exam + flight test. A possible short cut once sufficient experience for the ATPL is held is to skip doing the IR exam + flight test and do the ATPL exam + test only. The FAA ATP automatically gives IFR privileges.. .. .The catch is that this leaves you without an IR for the time it takes to get from CPL to ATPL.