The earliest example of the noun 'standout' given by OED is from 1928 (in the US), and Chambers Dictionary of Slang dates the adjective to the 1930s (also in the US), although the earliest non-hyphenated example of the adjective shown in OED is from John Irving in 1978. Chambers has listed the noun 'standout' (though not the adjective) since at least the 9th edition (2003) without any 'geographic attribution', so although it's a definite import it's been established 'over here' for well over a decade...