Ah alright. I have a tendency to leave bits unsaid because I assume that people can read between the lines, which I understand is difficult both over the internet and when you have no prior experience talking to someone and how they think.

I'll try to be precise. There's some theories in international relations that the hegemon controls international organisations, which is heavily debated and I personally find to be a weak theory. The first commenter is using this to frame the UN as toothless and under US control, which it plainly ain't. So stating that the UN is controlled by a single state is wrong. What is happening is that a veto player is effectively hindering everyone else from acting, but that is not control, it is obstruction.