I drive a 2023 Kida Rio 5 which is small, simple and fuel efficient (combined 40 MPG). Kia is killing it though, because not enough Americans bought them. They (Americans) instead buy the larger Forte. I specifically told them I wanted the Rio 5, and after a few calls they found one (1!) and proceeded to mark it up $2k - still worth it.
Not only do Americans tend to buy larger vehicles, but CAFE regulations encourage automakers to increase the footprint (area between the wheels) of the cars they offer. This is another reason the Rio is (and other small cars are) discontinued.
CAFE regulations (in a nutshell) require automakers' vehicles to meet a particular fuel economy per size of footprint, averaged across the vehicles they sell. So, they can meet the standards either by increasing the footprint of the vehicle, or by increasing the fuel economy of their vehicles, or both.
