After I did a little research through the net trying to find stuff that would help me in my history essignment, I came across this poster used for military propaganda at the beginning of the century.
Surprisingly enough, Uncle Sam seems a little yellowish than usual and for some reason it says "BertArmy". Could it be that Bert was trying to draft the public's opinion towards supporting him in a war against the US?

I think we'll have to dig up a little further in history to find that out.