Can a promotion be revoked after accepted?

To whom it may concern,

I recently demostrated my interest for a promotion within my department. Thereafter, I was offered that position, and I verbally accepted. Salary increase (50%) and effective date was also agreed upon during that conversation. The promotion was given to me by my manager, with her manager's approval (who later called to congratulate me). Ever since then, I've incurred new expenses counting on my new salary. In addition, the entire office was made aware of my promotion.

Two weeks later, I am being told that because of the company policies on promotions, I cannot be promoted until five months from now, and even then the promotion is not guaranteed. This promotion was offered by my boss' manager, who was the person who extended my initial employment offer, and thus I was fully under the impression that the promotion offered was properly carried out and with the proper authority.

Here's the catch... I am a US citizen, working for a US company OUTSIDE of the country. My employment contract was made outside of the country.

(1) Does the offer and acceptance of the promotion create a legal contract?
(2) Because of the fact that the employment relationship was started outside of the US, does an American court have jurisdiction over this, or do I have to bring the case to a local court?

By the way - The company is based out of GA.

Thank you