It seems like all the countries in the world are allies with US except those who refuse it and those that US are fighting against. Russia and China are the strongest adversary of US so far in my opinion, not to mention some of the little countries they are also allied with like the North Korea and other stubborn countries in middle east. But I think despite of these countries that cause stir to the world, America still holds the strongest alliance to keep the world stable so far, and that is its alliance with both the developing and developed countries all over the world, especially in Asia and Europe.