No it isn't

Oh my. It’s not all of us. I swear.

So- the point of the joke is that Americans are dumb... but the commenter says: “the Americans..” implying they are not themselves American- Americans usually say “Us Americans..” “We Americans...” or just “Americans” to refer to fellow Americans. “The Americans,” at least in my experience- has really only been encountered when speaking to people from other countries- it was particularly associated with Soviet era Russians and WW2 Era Europeans- a fact seen often in American Fiction, with the show “The Americans” title being a reference to that- the main characters being soviet deep cover operatives.