I'm not sure if this would have worked and I know it's not very helpful after the fact but most US Airlines who travel to points internationally have at least a few
published foreign telephone numbers. AA shoes the following number for The Netherlands: 020 2013 610
I'm not quite clear about exactly what happened. If your final destination was Amsterdam (an assumption on my part but it matters not where in the EU) you wouldn't need to claim your bags in JFK before connecting onward to Europe. Your bags should have been tagged in SJU (San Juan) to your destination as a flight from SJU to JFK doesn't require customs clearance. How did you know your bags were missing in JFK? Did you have a stop-over in New York?