Why USDC works for hosting in Spain
USDC is fully reserved and regulated, which suits buyers who want a stablecoin with published attestations. In Spain the alternative is a card billed in dollars against a Euro (EUR) balance. Local cards settle in EUR, so any foreign-transaction fee on a dollar invoice comes from the issuing bank.
Paying from a wallet takes the bank out of the transaction. The invoice is priced in US dollars, the USDC amount is locked for 15 minutes at the live rate, and the transfer goes straight to the address on the invoice. Nothing to approve, no merchant category to argue about.