Yep, Google or Wikipedia will show you just what monsters loco like the SD90's are. Some of the newer models from GM and GEC are pushing out 6600bhp from a single power plant.
It's not just the massive trains that the locos have to contend with; the US railroads tend to go straight over hills, rather than ease the gradient with cuttings and embankments. Result? A need for tractive effort that, when written down, looks like a lottery jackpot...