The US has fairly strong regulations protecting card holders from liability.
Regardless, the eShop is about as low risk as you can get, especially if you don’t have Nintendo store the card info.
You could buy a digital code for a prepaid card on Amazon.
How do I use my credit card on my Nintendo switch?
Select Shop Menu. Under Credit Card, select Save to save a credit card or select Change if a credit card has already been saved. When you change your saved credit card information, it will also change the credit card used for any active auto-renewal memberships (such as Nintendo Switch Online).
Is it safe to use credit card on Nintendo eShop?
Yes. You have the option to save the credit card information when you add funds or purchase content with a credit card in the Nintendo Switch eShop. Credit card information stored on your Nintendo Account can also be used for off-device purchases.
Why does my credit card not work on Nintendo switch?
Error Message: Contact Your Card Issuer or Select a Different Payment Option. A credit card charge was not accepted on the Nintendo Switch eShop or Nintendo.com. You receive the error message “There was an issue processing your transaction. Contact your card issuer or select a different payment option.”
Does Nintendo switch accept debit cards?
Yesas long as it says Visa/MC/American Express on your debit card.