How and where do we register a social network company with partners/co-founders in three different countries?

I co-foundered a successful social network company and we have a beautiful app and respectable number of users. I'm located in a small country in West Africa, my cofounders are in Eastern Europe. Considering the little funds available in our regions, it only makes sense that we seek funding in the US, especially considering the fact that most of our users are from US. The general arrangement is that the development and research team is in Europe and the Marketing and Business/Admin team is in Africa. This however creates a dicy situation because we're unsure on which country to register in. There's the US, W/A and Eastern Europe. Which one should be the parent company? Mind you we are a very small startup with no money and are bootstrapping. I'm of the view that we should register it as a US company with Africa and Europe as sub companies; but I have no idea how this works. How do we go about this whole issue to ensure that we have a nice structure.