Spouse excessively attached to mother, no communication, lives abroad. How to get him back?

It must feel quite painful, having communication cut off by your husband. I'm glad you're reaching out for help.
From my stance, an overly involved mother-in-law can be a problem in a marriage, yes, however, putting this across to your husband in a way that didn't offend him would have been more important. Accusing him or his mother could have resulted in a negative impression on you.

Your husband sharing your private conversation with his mother is inappropriate if it makes you uncomfortable, however, voicing your thought non-accusingly in the situation would have been more appropriate.

I think that you should initiate a conversation with your husband or his mother through whatever medium possible and re-start a gentle conversation. It would help the situation if you voiced your expectations and concerns of the marriage rather than point out each other's flaws. If it works, apologize for feeling threatened by their relationship and instead ask your husband to invest in your marriage as sincerely as he invests in the bond with his mother.

Sometimes, putting aside right and wrong and giving things another chance from a different stance can solve a lot of seemingly big issues.

You can also seek some help with a counselor/ mental health professional who can better guide the formation of your new perspectives and equip you to give another honest shot to your marriage.