I’m not convinced that the majority of international students necessarily target US schools for the “breadth” of the education as opposed to the prestige and the desire to live (and perhaps eventually work) in the US.
In countries like Singapore and Hong Kong that have close historic links to the UK, the educational system values specialization (i.e. the standard is A levels). But given a choice between the UK and the US, many students and parents feel the US is more appealing. And it’s harder to get in when the educational system doesn’t emphasize ECs, adding to the prestige of admission.