Alt text: Meme caption: "When you forget to bring your reusable bags to the grocery store", below is an image of Dexter from Dexter's laboratory weeping as he strokes a picture of the earth, saying "I have failed you!"
Taking garbage from 1000 plastic bags into account is exactly what it does.
You're underestimating just how much is needed for a cloth bag.
From growing the cotton, to processing it, to making the bag. That's a long way. There are a lot of steps involved. A lot of energy required.