Britain’s The Guardian offers up a series it calls “Great Poets of the 20th Century,” a link-rich glimpse into the English public intellectual class’s image of itself. American readers may be surprised that the editors claim America’s own Sylvia Plath for England (anticipating, I suppose, the outcry that would have greeted their inclusion of Ted Hughes without her) and mysteriously elevate Sassoon over Owen. Still, it seems well worth reading. Eliot and Auden have already seen print; Plath, Larkin, Hughes, Heaney, and Sassoon will follow over the next few days.
Joseph Hutchison, Colorado Poet Laureate 2014-2019, has published 20 collections of poems and edited or co-edited three poetry anthologies. He currently directs two master’s-level programs for University College at the University of Denver: Professional Creative Writing and Arts & Culture Management. Joe lives with his wife, Melody Madonna, in the mountains southwest of Denver, Colorado, the city where he was born. 
Since every poet on this "great" list has a firm connection with Britain, I highly doubt that it’s mean to represent "great poets in the English language." Otherwise they might have shoehorned Stevens in, or Williams, or Frost, or Bishop, or …
I don’t think the series is intended to be ‘Great English Poets of the 20th Century’, but great poets in the English language. Nobody’s claiming Plath (or Eliot) is anything but American.