have we "imperialized" the Neapolitan pie?
Have Neapolitan pizzerias in the states created an (almost) entirely new product as well?
I don't think either of these is a fair assessment. In the pictures you posted, to say nothing for Norma's, I see a great deal of variation. It's not like pizza looks one consistent way in Naples and different but consistent way here. Nor is the look of the pizza here unprecedented in Naples. For whatever reason, Americans have gravitated more towards the da Michele look. Maybe because it is more visually stunning and different from other styles common in the US? Maybe people saw Julia Roberts eating the da Michele pie in Eat, Pray, Love and so that's what they expect from NP? In any case, I think the sub-style that is predominant in the US is largely driven by a desire to deliver on the customer's expectations more than an attempt on the part of the pizzaiolo to create a new product.
Notwithstanding, like in Naples, pizzaiolo have a signature look to their pies here as well. Mathieu's pies don't look like Paulie's pies don't look like Anthony's pies, don't look like my pies, etc. (I'm honored to be included in that group, BTW). The center of the bell curve may be tighter, but the overall range is about the same. All NP here is not leopard spotted. Luzzo's (albeit coal) looks somewhat like the Trianon pie in the slice article. Plenty of places put out pies that look like the Port'Alba pie in the same article though I suspect the Port'Alba pie is a lot better than the blond pies served here.
It's an interesting question, but IMO, the difference is largely driven by a tighter expectation for NP here than in Naples.