How can I get my H1B refundable security deposit back from my ex employer?

I came to the U.S.A on H1b visa and my company has sponsored my visa. But they took a refundable security deposit through its sister company B located outside the U.S.A through a savings bank account outside the U.S.A. I have the email which says the company wanted the refundable security which would be paid back to me after 3 months. I also have my savings bank passbook which shows the account number shared to me by my ex employer and the amount debited. But now even after a year has passed, they are refusing to refund the money taken from me. I am planning to approach the civil courts. What proof should I keep with me to show the judge and convince him that my ex employer owes me money that they took outside the U.S.A. Are there any chances of getting my money back through the civil courts in the U.S.A?