It was not a mistake, and it was not america-specific. The "clears its orbit" criterion is exceedingly difficult to measure (it was evidently very hard to apply within the solar system; it's going to be impossible to apply outside it) and leads to absurdities (the same body may or may not be a planet depending on where it happpens to be). The distinction between bodies in hydrostatic equilibrium and smaller bodies is clear, natural and valuable; the distinction between bodies that have cleared their orbit and bodies that have not is none of those things.
