Luz....LOL, DONUTS? Hello, donuts do not fall under the category of "desserts!!" When was the last time you had dinner in someone's home and they served donuts for dessert? Check any and every menu ever printed and I am certain that "donuts" are not listed under DESSERTS! They may be on the menu & available during the breakfast and/or lunch times.....but donuts are basically a breakfast food, especially as an accompaniment to coffee, tea and Hot chocolate. The Simpsons can do what they want....they're make- believe and very weird. LOL
As for an iconic American dessert......ever heard the expression "It's as American as Apple Pie ?"....and some people change that original expression to Blueberry Pie or Cherry Pie, etc. It's safe to say "Pie" qualifies as an iconic American dessert.
If one suffers from an incurable sweet tooth,dessert can be anything! Yeah, I suppose if you INSIST...even donuts! LOL