“The United States is bound by a number of treaties that could, in theory, force it to get involved in a war if an ally is attacked. Consider, for example, the situation in Ukraine, a non-member of the North Atlantic Treaty Organization. If a NATO ally were to find itself under similar threat from Russia, the U.S. may find itself duty bound to war.”
Source: Map: The U.S. is bound by treaties to defend a quarter of humanity – The Washington Post
