One thing to bear in mind, if the student goes to a JAA approved school in the USA then the examiner is *probably* a Brit / European who examines outside of the FARs i.e. as far as the FAA is concerned, the flight is probably an instructional dual flight unless the JAA examiner is also an FAA examiner - they would have to be IMO at least an FAA FI. This means the FAA has no control over the standards of students passing a JAA flight test in the USA.
Therefor the blame should lie wholely with the CAA for not enforcing proper standards are met during their (expensive) approval inspections and they should call suspect examiners in to answer for it.
If the PPL is FAA, in my experience FAA FE's are very stringent in the examinations (it is their neck / income on the line) and will only pass a student who meets the FAA requirements. FAA PPL syllabus is different to JAA, and includes night flying as well as other ground reference manouvres and their log book may reflect this.