If I can no longer afford to pay alimony, can my ex have it taken out of my social security?

I am so sorry for your situation. While social security benefits are protected from most creditors, they can, unfortunately, be garnished for alimony payments.  I know that you say that you have no way of getting to the United States to deal with this.  Is there someone that you trust that lives in Hawaii - or where the order was entered - that you could give a Power of Attorney to to bring the motion to modify the divorce agreement?  Just get him or her the document that you will need to prove your claim and your condition.  There has to be a substantial change in circumstances for modification in most states.  Good luck to you.