Broderdorf said the changes reflect input from customers.
"The vehicle should be quieter? We've added laminated glass throughout the vehicle," he said.
"On the Stelvio, before, we used to have plastic cladding down below. Why? It's a premium vehicle; it shouldn't be there! Let's change it to body color and drive home the premium feel of the vehicle."
The product modifications for the 2020 model year are common to Alfas sold globally.
The brand returned to the U.S. in 2014 after a two-decade absence and peaked at 23,800 sales last year.
Volume is now high enough to merit a ranking on J.D. Power's Initial Quality Study. This year, Alfa ranked fourth from the bottom, ahead of Mitsubishi, Land Rover and Jaguar.
This year's U.S. sales decline through September meant only 13,347 deliveries. Broderdorf said "the volume segments are the ones that matter, as much as I love the specialty cars" that were part of the 2018 product plan.
"My core focus in the short term are products like Tonale," he added.
Asked if there was a chance Alfa Romeo would be pulled from the U.S. in light of the proposed merger of FCA with France's PSA Group, Broderdorf said: "The plan for Alfa Romeo is rock solid, and we will continue to grow, one sale at a time, one consumer at a time."