Hi Ahmed E,
It's nice to see you in Community. Welcome! I can understand the benefit of being able to have your products set in U.S. currency by default. However, there isn't a way to add a default currency for the COS in another currency, at this time. I do encourage you to submit a suggestion for future updates. Our Development Team appreciates customer recommendations, in assisting them with improving your overall customer experience with QuickBooks.
If you have any other questions, please don't hesitate to reach back out. We would be glad to help!