Why Revolution Must Start in America
This is plainly going to be American exceptionalism, for good reason. America has been the most productive economy for the past hundred years. The productive forces in America are very well established. If a dictatorship of the proletariat was able to fully utilize the industrial capacity of America, material abundance would be stronger than in any other developed nation, barring perhaps China.
Moreover, America has been the biggest counter to any sort of communist movement worldwide. America has covertly toppled many even reformist regimes in various nations across the globe in an effort to stop communism. If a revolution occurred in America, it is uncertain if any other world power would even have the capacity not even to crush the revolution, but to just intervene. And America wouldn't be able to support a grand anti-communist military operation without a stable domestic front. With mutinies, strikes, supply-chain stoppages, and other such events, any attempt at stopping an uprising would be extraordinarily prolonged and difficult.
America's geography is advantageous in this regard as well. Isolated by two oceans, desert to the south, tundra to the north. Any attempt at stopping the American revolution would need to cross this terrain. This isn't even counting America's nuclear arsenal and the biggest navy in the world, which would then be in the hands of the revolutionaries. America could develop socialism and then communism in total peace. Or, instead, carry the revolution across the world before it can successfully mobilize. The size and strength of the American Military Industrial Complex in the hands of the revolution would be nearly unstoppable.
Given how much debt the United States has taken on, a successful revolution in America, or even a failed one, would likely crash the global economy and take decades to recover. An economic crash when there's a workers revolution would only lead to further unrest and possibly more revolutions in other parts of the world.
While the revolution may not happen in America, America would be the greatest possible place for the revolution to occur. The geography, the industrial capacity, and the military dominance of the United States not only would be important to have in the hands of revolutionaries, but the removal of the United States government from the list of counter-revolutionary forces would be greatly beneficial.