In here we were expected to be able to identify all countries of Europe on a map too, yeah. I'm inclined to say that kind of geographical knowledge is far more useful than being able to list the presidents / kings / rulers in order, though - at least when this listing in order is a goal in itself, instead of merely a consequence of having a thorough knowledge of history (which is obviously not feasible in third grade). More important to have a good idea about, say, the Revolutionary War, the War of 1812, the Monroe Doctrine, the Mexican-American War, Manifest Destiny and things like that (to limit myself to older history), while only knowing the most important presidents, than to be able to rattle off the full list while not knowing much else.
Mind you, we did the same thing in primary school, with kings (not PMs) of Belgium, but there were only seven of those, eight by now, so it isn't exactly a long list to learn.
Of course, in the internet era where all this information is just a mouseclick away, having an extensive general knowledge is becoming slightly less important - but you do need to know some things, and perhaps most crucially, you need to be aware of what you know and what you don't know. What I find much scarier than Americans not being able to list their presidents or even not being able to find all their states on a map, is the absurdly high percentages in those surveys who estimate the population of the USA at half a billion, or a full billion (or, at the other end of the scale, at a hundred million or less). Because then their whole worldview, which translates into their political views, is based on completely wrong data about the position of the USA in the world.