I've been playing with Hetzner since June. One of their billing options is PayPal, which is what I've been using. That should come through as a US charge. Note: their PayPal option isn't a recurring payment; they send you an invoice each month and then you have to go into the billing page and pay it via PayPal. It's kind of tedious, not sure why they set it up like that.
P.S. before I put FastMail on my credit card, I used to have it on my bank debit card. My bank charged me some silly international fee, like $5.00 or something just for the privilege of using my own bank account, but I never had an issue with the actual payment. If possible, I recommend putting FastMail and Hetzner on a credit card and then pay the credit card with your bank account.