I had no problems subscribing to stuff through wise or revolut cards. Both are prepaid as far as I'm concerned - they won't let me spend above my account's balance.

AWS will likely write off most costs automatically, but if you truly do manage to rack up a $50k bill somehow, you're getting sent to collections and/or their legal team.

The terms you signed obligate you to pay your balance. Whether your credit card works or not doesn't negate your legal obligation.