There are so many global affairs goin on that can put US into jeopardy.

1. Uprising in middle east - US can influence to build/oust government but cannot ensure stability and hence safety for itself.and its allies.
2. Iran nuclear program: US cannot go to war because of Russia, China and obviously other muslim country will grow more hostile. And they still need to mantain relation with Israil at any cost. Israil however is growing restless over the situation.
2. China/Japan conflict over an island - US cannot take sides because Japan has been its ally and Japan army is synonymus to US army while US cannot afford to antagonize china at any cost.
4. Domestic and international hatred crimes. They cannot offend any religion not only because of their belief, but for ending war in Iraq and Afganistan. This war can turn into religious war at any time. Just look at their reaction to death of one of their ambassador.

Did not know US was such a big part of global politics. Personally, I am finding these way more interesting than non-ending bullshit going on in Nepal.