the good thing about an FAA multi is that is valid for life, JAA requires a class retest every 12 months. What an airline will be looking for is the number of ME time, not if it was done under a JAA or an FAA license. I suppose that in the future you might want to come back to the US and fly some more Multi because is cheaper.
Also, do not say "JAR recognised" for Night and IMC. Night and IMC is not a "JAR qualification", it's a National UK qualification valid in the UK ONLY.