SEPA - Countries not using IBAN

Hello,

due to SEPA implementation it is necessary to provide IBAN code in bank accounts.

We need to massively inform IBAN field for many bank accounts.

As far as I know, SAP does not provide any tool to automatically or massivelly complete IBAN data because:

-there is no directory or file that SAP can use to perform a massive load.

-SAP does not calculate IBAN, because considers that only banks can provide IBAN code from the account number.

Therefore, we need to create a tool generate IBAN code:

-that checks if it's necessary to create IBAN or if it's already created.

-updates IBAN in master data (eg vendors)

-those accounts are from different countries.

My question is:

How can we do for bank accounts not using IBAN code (for instance the United States)?

What's the 'behaviour' for vendors not using IBAN, in a massive load or payment using SEPA?

Thank you