You couldn't be more wrong about this. The decentralized Vietnamese beat the (by-then) bureaucratic US.
The US army during WWII was defined by its ability to delegate to the lowest possible level of the officer hierarchy and this was one of the major reasons it was able to beat the rigid and highly-centralized Nazis.
The Confederacy came within a stones throw of winning the Civil War, which would have been the equivalent of two guys in their garage taking down one of the worlds largest Corporations. They lost because of the overwhelming differences in resources, but their agility and ability to promote talent allowed them to run circles around the North for the first two years.
Winfield Scott and Hernando Cortes both won in Mexico because they distanced themselves from their respective governments. They were allowed complete freedom from bureaucracy because they went out of communication range of the politicians.
Sun Tzu actually made a name for himself by beating a major neighboring kingdom with a tiny, but agile force.
I could keep going...