The "really big" locomotives were the SD90MAC and the GE AC6000CW, both at around 4500 kW. In both cases, U.S. railroads decided that these giants resulted in having too many eggs in one basket, and they reverted to multiple units of the smaller model engines.
Union Pacific 7125 is an AC4400CW.
As far as I know, the US trend to abandon the 6000HP locos was related more strongly to two other factors: (1) frequent breakdowns due to problems with the engines; (2) the issue I mention for Europe, wheel slip in non-ideal weather conditions.
It is worth to note that at least EMD's AC electric equipment (inverters and motors) also originates in the German development: via Siemens who made the first few. (GE's is all own development, though, I believe.) *Lunatic*, n. One whose delusions are out of fashion.
