Does the US also have a frozen ATP like we have in Europe?
We don't have a 'frozen' ATPL in Europe either. We have a CPL/IR with an ATPL exam pass that is colloquially referred to as a 'frozen' ATPL....
In the US they observe ICAO, you get the hours, you take the exam you get an ATP Certificate. JAA/EASA Gold plating of 500hrs multi crew not required.