I don't think America (as a collective) "wants stupid Americans", I think people are generally of the mind that "intelligence is good". Unfortunately, I think what that means is largely subjective in many cases, and tends to be aligned with their own interests/preferences.
My suspicion, which is mostly just me thinking out loud and is based on no real evidence, is that folks are (a) largely desensitized to stimulation due to aggressive "marketing" (in the loosest sense of the word - whether ads, click/viewbait, or other quasi-exploitative attention-grabbing things); and/or (b) have observed that, culturally, a lot of "dumb shit" is mainstream enough (in terms of critical mass within their social microcosm) to warrant conformity, and thus may be a preference that is adopted for identity or inclusivity purposes. Similarly, it may be seen as a pathway to some form of success or recognition (see: IG/YT influencers, tiktok fads, etc).
I'm sure other, much smarter folks have actual evidence or have performed studies (and I would be interested in learning more), but based on my personal experience, the above seems to hold true, generally speaking.
Asking the important questions.