@threalist America is and always has been an unreliable ally.
Any commitments made by America have a 2 year expiration date due to the fact that the House controls the money, and gets reelected every 2 years. Ask South Vietnam about that.
America has used the enemy of my enemy is my friend strategy, ever since the Revolutionaries got money from France.
All of America's external promises are based on domestic politics, and can end when the political wind changes direction inside the USA.