Canadian poutine eater here… IMO sadly there is no substitute for the curds. They are just texturally unique. It’s quite important considering it’s one of only three ingredients.

I know your pain though, I was living in the states for a bit and it was basically impossible to get good poutine. If I wanted it I had to make it myself, which meant a long trip to Tillamook to buy cheese curds from the source direct.