There is a history of observation that posits that the US is "agreement incapable," such as in its long trail of broken treaties and promises, and even in terms of its modern geopolitical agreements and maneuverings.
Part of this is due to the modern construction and machinery of the state, and the fact that "the US" is an abstraction, that though believed in with a measure of stability and continuity - the dollar continuing on as reserve currency for example, though that is quickly coming to an end - doesn't properly convey its messy and chaotic nature as a geographic location of a vast diversity of and oftentimes explosively violent convergence of global historical forces.
The ever-shifting machinery of the US State - though meant in part to deal with this violent convergence and absorb some of its shocks - ensures an ever-shifting balance of factional struggles as well, with an oscillating expression of domestic and foreign policies, which like an electrical current, can prove generally useful, but also quite dangerous if disrupted.
This doesn't fully account for the US' unique set of geopolitical behaviors among its constellation of modern state brethren; the position of hegemon better accounts for this of course, both with the behaviors required for hegemonic control and maintenance, and then with the corruptions that that power affords.
Nevertheless, accountability in the usual sense given this state of affairs is an elusive and slippery thing.
