Hi,
Check the currency of credit control area that is assigned to company code .The path is SPRO->Enterprise structure->definition ->financial accounting->Define credit control area. Here maintain US and then try.
You may need to check OSS note before changing the currency as the change may impact the already created documents.
But Currency can use from only Company code and Customer Currency and you can maintain only with Currency Conversion Exchange rates in OB08
Regards,
Vikas