You did not lose the $30. Once redeemed, the balance stays in your Microsoft account and normally does not expire.
The issue here is the region mismatch. Your $30 balance is in USD/US region, while your Microsoft account is set to Lebanon. Changing the Windows region to US does not change the billing region of your Microsoft account.
Microsoft account balance is region-specific and cannot be transferred or converted to another region. This is why you are getting PI-InternalError and cannot add the billing address.
If you actually live in the US now, you can change your Microsoft account country/region to the US and add a valid US billing address:
If you are still located in Lebanon, I would not change the region simply to use the US balance.