If you are selling exactly the same product as others, you can only differentiate yourself from the other in

(1) Price (Product, Shipping, Warranty ...)
(2) Service (Reputation or Relationship)
(3) Location (Convenience)

So long as you can differentiate yourself from the other in positive way, you can still create USP. But it will be easier if you have a product that is unique to your company even if it is based on the perception only.