Does the US on average have more than 50 people per square km? Nope, it's somewhere around 30. I'm not american, but it's easy to see that other than the big cities, most of the US is pretty spaced. Alaska? Farmland? Rocky mountains? On the other hand, I know for fact Bangladesh has more than 1000 people per square km on average. Something like one third of their population actually owns any land, so it's fucking packed over there. Don't even think the US is remotely crowded.
Not being a bitch or anything, just I happen to know some facts because I've been doing this stuff for months in Geography and just wrote a rather large paper on Bangladesh... So that chart thing is pretty accurate.