JoeF said:Stamps from other countries, of course. There is nothing special about that.
But he won't get stamps from US officials when he enters the US. Just like I, a citizen of a country of the European Union, don't get any stamp when I travel from the US to any city in the European Union.
Not to argue with you, but if you visit the page, you'll see that those are US entry stamps and he is a USC. Since he obviously collects them, maybe he asks for his passport to be stamped.
Like you, I also have a European passport and they never stamp my passport unless I ask. So I understand your point.