Also, the financial aspects of the ISS are one big nightmare, since there is no trading of money between the countries, only of hardware and laboratory time. That is why there are so many cargo spacecraft, and so many different modules and other components. While the USA carry most of the costs and thus have most of the hardware and most of the lab time, others are also represented that way, and the changes because of module cancellations or the Shuttle retirement also had to be represented by non-financial means.