Eyskens, that's a rather famous name here in Belgium. We have had two ministers (father and son) in Belgium. The son, Mark Eyskens, is still alive.
I think you should check the arrivals lists at Ellis Island, or perhaps passenger lists around '20 to NY. Sometimes more information is available. Your ancestor John (Jaan?) Eyskens might have been called Jan (more common here in B, or his christian name Johannes). Good luck!