It's true that the UN isn't really efficient. How could it be? It's 200 countries with vastly different cultures, ideas and goals. Getting all these powers to agree on something is bound to be hard. But that doesn't change the fact that having a common forum to talk in is a fundamentally good thing. There's also no alternative. The US has been trying to impose their will on other countries by force or political/economic power for decades, with decidedly mixed results. It's actually easier to find a compromise and get everyone to act on it.
Politics is hard. Remember that the next time you can't get your family to agree on dinner.
Regarding social security, every EU country spends more (as % of GDP) than the US on welfare, thus making cuts more likely. If unemployment benefits are cut, the unemployed have to switch to cheaper cigarettes. In the US, they die. In numbers: the unemployed in Germany get 60% of their last income (67% with children) for up 36 months. After that, they get about 400$+rent+heating+ electricity. In the US it's 3x% for a few months, and apparently not even food stamps after that.
Others call them children