There is a very easy workaround this message that doesn’t requires using any proxy or VPN. Visit https://wallet.google.com and sign in with the Google account for which you wish to redeem the gift card.
If you’ve already specified an address in your account, then open Settings (gear icon), and edit the Home address. In address, you need to input a valid US address. You can use your relative’s address living in US or Google HQ address itself as shown.
Those who haven’t specified an address earlier would be shown this page. Select ‘US’ and enter the US Zip code to proceed.
updating the address, visit the redeem page https://play.google.com/redeem and you should see the "Redeem your code" webpage with a field to input the code and redeem it.
NOTE: After redeeming, your home country (United States) cannot be changed if you have any Google Play balance remaining in your wallet. No expiration dates apply to the gift card.
You can later check the Google Play balance by visiting the redeem page or from Payment methods tab in your Google wallet account.