In 1994, the U. S., U.K., Russia, and Ukraine signed the Budapest Memorandum on Security Assurances. This stated that in return for Ukraine giving up its nuclear weapons the signees would give security assurances against threats or use of force against the territorial integrity or political independence of Ukraine.
Russia has obviously violated this. But what about the U.S and the U.K.? Shouldn't they follow through on their assurance of protecting the political independence of Ukraine? Have they done enough?
Today's U.S. reponse is that this is not an official treaty, so it is not legally binding. It doesn't lay out any specific measures to insure that security. I doubt Ukraine feels that way. They got screwed by the U.S and U.K. And why would any other country agree to give up its nuclear weapons(like North Korea), knowing that the U.S. promises are worthless. Iran nuclear deal? Iran could sign any document and not keep their promises because the U.S. doesn't keep theirs.