> Is there some kind of objective analysis which supports this claim

It's a bit hard to have objective research on marketing and public perceptions. But how else do you explain all the marketing in that regard, and the fact that Americans, on average, even urbanites, keep buying massive pickup trucks, the majority of which are never used for anything more than a commuter vehicle for 1, maybe 2 occupants? Even in rich countries with very outdoorsy people (Switzerland, Nordics, hell, the Netherlands has camping as a national sport, and during summertime they do mass migrations in towed campers and campervans towards the south of France, Italy, Spain), very few people buy trucks.

Marketing, an arms race, manufacturers not offering much else because their marketing works, Americans being very aspirational about what they'll do with their vehicles, idk.

> It's hardly an American manufacturer thing, either, Japanese cars have reliably gotten bigger year after year as well.

Japanese vehicles in the US or everywhere? Cars in general have been getting bigger because of safety features, but American monstrosities with lower visibility than literal tanks are an almost uniquely American phenomenon (slowly invading the rest of the world too).