I have previously posted here an examples of Portuguese immigrant who had to register for the draft in World War I.  Now as I previously explained it was a shock to find this draft card because he was not an American citizen.  Ancestry.com explains in their “interesting facts” section under the source for their World War I Draft Card Database that:

Non-citizens were required to register but were not subject to induction into the American military.

So although John Paul Silva registered, he would not have been subject to induction.  I found that to be interesting!