The Sacoolas case has gotten pro forma coverage in the States. Most of the major news outlets (CNN, NPR, etc.) have run short stories on it, but the vast majority of people here haven’t noticed. No one is talking about it.
The issue of diplomatic immunity is a tricky one. On its face, it seems as if it doesn’t apply here, but it’s a technical legal question, and the stories I’ve seen haven’t included the details necessary to make that determination. One thing to note, diplomatic immunity belongs to the government, not the person. If the US government waives or drops the immunity claim, Sacoolas is subject to extradition, and she can’t press an immunity claim on her own.
There was a similar case here in the US in the 1990s. A Georgian (IIRC) diplomat was drunk and drove up on a Washington, DC sidewalk, killing a pedestrian. The US government pressured Georgia to waive diplomatic immunity, which they did. The diplomat was tried, convicted, and served a prison sentence in the US. In this case there was no question about the applicability of diplomatic immunity, but Georgia waived it. I was living in the DC area at the time, and the story got a lot of coverage, at least in the region. It was a big deal, especially controversial was the pressure put on Georgia to waive immunity, something that almost never happens.
Also, the whisking away back to the States of a diplomat or US government employee/contractor who commits a crime is standard practice. (When I was working in the Hague the briefings on the subject were in the context of refusing to take a breathalyzer test if pulled over for erratic driving. Diplomats could refuse without penalty from the Dutch government, but the US government would put you on the next plane back home.) Of course, parking tickets aside, diplomats are a pretty law-abiding lot. Rarely does a diplomat commit a serious crime, much less one involving someone’s death. It’s done to avoid a diplomat being thrown in jail in a place where the legal system is a sham (I’m not talking about the UK here) and the government having to press a claim of immunity to get them out.