This seems very very odd, specially since Stripe supports that feature by default. Stripe has an integrated VAT check capability so when you enter your VAT number it will check if its valid.
Can it be that your VPN, adblocker or similar are preventing this? (some adblockers remove certain calls to the API that Stripe uses for this)
Here is the proof. It works with various countries, tried several different countries across the world.
Note, a TIN is not a VAT number, so this should not be mixed.
@danperks can Cursor sort this out internally? seems like they arent aware of that capability?