Hell yeah! That will make a porter that I would very happily drink. A good porter should have a meaty portion of brown malt in the grist. You are a good person!
However, I'm not sure that I would call it an American version of the style. I learned to brew in the early 90's during the micro explosion that happened in the Pacific NW. I can assure you, brown malt wasn't available when the style was created. At the time, there seemed to be an agreement that black malt was the defining feature of a porter and black barley made stouts stout.
That is complete rubbish.
At the time, nobody knew anything about anything. And that's the key thing to know about American Porter--it's kinda made-up BS. Why? Because the knowledge, malts, sugars, etc needed to make an actual porter weren't available.
Your grist suggests that you've done your porter research, your big dose of brown malt proves it. Unfortunately, an American Porter isn't a proper Porter, so I would suggest that your current grist will shoot wide of your mark.
I would suggest googling the recipe for Anchor Porter. It is, after all, the original (modern) US Porter, and I'd argue one of the best.
Deschutes Black Butte Porter is another widely available recipe that defines the style.
My personal favorite was Bridgeport Porter. But their quality control was all over the place. When it was good, it was amazing.