Eve Probably easiest is to go to https://transferwise.com/ and use their service to send money to your bunq account. You can easily pay with a US credit card, or ACH transfer and several other forms of payment. Initially some KYC procedure might be needed but afterwards it's very fast. I have a friend from the US who uses it sometimes to send money to their bunq account and it's almost instant.
Edit: As Volker mentioned, PayPal might also work fine. I just don't have personal experience with their service when it comes to sending money across the pond.