This is a very interesting question, especially if you expand the discussion to include Turtledove.
Although both authors have their detractors on this board, I'd wager that without the influence of Turtledove - even more than Sterling - this board might not exist at all and, if it did, it would be much smaller.
While I count myself among one of Turtledove's main detractors as a novelist, his main AH series created PoDs and explored divergences that were pretty unique at the time of their writing.
We might decry HT's tendency to project real historical people into his timelines or present some AH events as little more than our history with the names and locations changed, but the basic premise of the TL-191 series remains fascinating and plausible: What would be the long-term effects of CSA independence achieved in part due to British and French involvement? To this day, I consider his central conceit that the US would find itself drawn into an alliance with Germany perceptive and plausible, as well as the probability that this would make any European war automatically a world war with major combat occuring in the Americas as well. His presentation of the US in this war as a somewhat prussianized, a bit less democratic, and very militarized nation also is plausible. In fact, from sports and socialists to race relations and economics, he paints a very plausible portrayal of a 20th century far darker than the one we inhabit. Too bad he tells this story through so many incredibly wooden and repetitive POV characters.
Again a good point. With Turtledove though I get the sense that the nature and rate of his writing - idea, brainstorming, notes, collating and spell-checking, publishing - makes it very different. There's less a sense that there are roads left untraveled - he just writes so much so fast. The bigger question with him would be - what would this place be like without him? Alas, though, the answer is likely "boring and obscure."
Of course if you know of an alternative direction he could have gone, please do tell. If there was any truth to the conceit that Turtledove originally intended the Great War to be an Entente victory, with the US being the Nazi parallel, that would indeed be fun to read. Or write for that matter.