Mea culpa. Mostly. I relied on Wikipedia's characterization of the E2 series as similar to the Bombardier CSeries which was the subject of the American tariffs

Mea culpa. Mostly. I relied on Wikipedia's characterization of the E2 series as similar to the Bombardier CSeries which was the subject of the American tariffs you reference. But the CSeries in fact became the A220, significantly smaller than the A320, so neither would it have been in the same category as the 737. Both the E2 195 and the CSeries are well above the threshold of 100 passengers that Wikipedia uses as the maximum for a "regional jet", with the former holding up to 146 passengers and the latter up to 160. However, this is well behind the 737 MAX at 220 passengers. This classification apparently varies by source; 49 USC 41714 considers the maximum to be 71 passengers, while some sources take a threshold as high as 150 seats. In any case, Embraer has gradually ramped up the maximum seating capacity on its planes, though you correctly point out that it has yet to take the middle-seat plunge.