One thing is clear that having a EU ATPL groundschools done you are most certainly better prepared for airline flying that your counterpart in US with a single written, which I took without ever opening a book ( Got 98% ).
Most of the pilots I have worked with have never even seen a ICAO flightplan form let alone now how to fill one.
While in EU advanced meteorology, navigation and airlaw is included in the frozen ATPL courses. Here it is customary for the airline to provide you with that training when you need it, say before you move to fly international trips.
Regardless, I find qualified pilots on both sides of the pond as well as persons that should have absolutely no business in the cockpit.
JJ