I have a hunch their main concern is this kind of marketing on your site:
"Access the American market
Our credit card comes with a U.S. billing address, so you can unlock features restricted to the U.S or Western markets especially if you don't live there."
Stripe might not even be allowed to say the reason if they brushed up against anti-money laundering policies. This is probably the exact reason for the ban, and the reason they wouldn't talk to the company about it.
"Access the American market Our credit card comes with a U.S. billing address, so you can unlock features restricted to the U.S or Western markets especially if you don't live there."
https://justuseapp.com/free-trial-card