Do you think they're out there shooting people in the Middle East so that Middle Eastern oil companies can make more money or so that the American ones can?
There is a vast system of interests, but I don't agree that overall incentives are to make US companies get as big as possible. They lose competitiveness at some point.
Middle East is not relevant.
Github not being part of Microsoft could be better for the overall economy. Consider the development of the World Wide Web. If you consider Github and aspects of Github as a network and communication protocol, it would be better in the long term to decentralize control.