I have not heard that ATM (debit card) does not work in Japan and I have not had such experience in Japan. I have ATM debit card from Bank of America which worked in Japan as long as I had the card, now more than ten years, and worked as recently as this March.

I think this is specific to the policy of your credit union, not general situation of non-Japan issued ATM debit card use in Japan. As long as your credit union does not change a policy of use of restriction in Japan then likely there is norhing you can do.

If able to use your ATM debit card in Japan is important to you then posdible that only solution is to get ATM debit card from another bank.

From my experince and experience of people I know most banks in the U.S. allow their ATM debit card to be used in Japan.