But in high school history classes, why should foreign countries devote particular attention to early American history? I believe I had a handful of lessons about the American revolution, and it's possible the Civil War was mentioned at some point, but other than that, we only really devoted any attention to American history at the time when the US was actually a dominant world power, i.e. post-WW2 (and to some extent in the interbellum).

I imagine it's much the same way in Britain and other countries. A country like mine is rather open to foreign countries in many ways, including in its history courses, but still the main focus was obviously going to be on European history, and the history of our region in particular. Early US history with little relevance for us or for Europe doesn't really belong there.