I do not know the specifcs of what the requirements are for each region, but there are plenty of articles online from variety of sources discussing the matter.
Heres the first few that came up in google ranging from 2009 to 2020
Car safety isn't just about protecting vehicle occupants. Automakers are now changing their Vehicle Designs to improve Pedestrian Protection and reduce injury in Pedestrian Accidents.
www.edmunds.com
Higher hoods and taller noses are just the start.
www.caranddriver.com
In recent years, car designs have seen a proliferation of blunt front ends, high hoods, and the “reverse teardrop” shape on many three-box vehicles.
www.google.com
That's interesting. I was not aware of the requirement that 0.8" in space be left between the underside of the hood and the top of the engine presumably to offer some hood crumple when hitting a pedestrian. However, that's the only specific requirement I see in those links. I would think most vehicles had met that requirement anyway. As for the rest, raising the cowl has not deterred designers.
Car & Driver implied that the 0.8" requirement results in higher a cowl, and thus higher seats and thus higher beltlines resulting in a bubble-headed appearance. Well, many models have had their belt lines raised more than necessary, slating upward from front to rear into a small rear window. That's a design choice, perhaps making new look lemonade out of a little lemon, facilitated by driver assistant tech to compensate for the resulting poor rear visibility.
C&R's bubble-head assessment 10 years ago doesn't seem to have panned out or at least is not considered a negative. Tastes adapt to new styles. And it sure doesn't stop C&R from differentiating attractive bubble headed sheet metal in today's vehicles from the "controversial".
And still, 2-box designs never went away with that requirement and you get variations in between the boxes, bubble-heads and wedges.
The rest is voluntary it would appear, each automaker doing their own testing with no established benchmarks other than their own. Of course their biggest fear is the NHTSA starting to dig deep in the data, doing extensive crash testing on pedestrian dummies, and rating cars on pedestrian friendliness and implementing more regs. So good faith token efforts are in order, some of which were noted in one of those posts--flush door handles, spring loaded side mirrors, whatnot.
In the end, you have a choice between a Ford Escape and Ford Bronco in the same size class, quite different looking vehicles, conforming to expectations of what road vs. off-road vehicles should look like.
Or check out Kia's line-up of Soul, Seltos, Sportage and Niro, all jammed together in a narrow sub-compact / compact group. They look quite different, do they not? And yet none of them are high volume sellers.
Compare to back in the day when sedans were king. If you wanted a compact or mid-size Toyota you had a choice between a Corolla or a Camry which looked alike except one was a little bigger and they didn't look much different from Civic or Accord. And that was when Toyota was selling something like 900,000 of those models per year. Those models are still being made and now there is the additional lineup of SUVs to choose from.
For whatever safety requirements, pedestrian or otherwise, that have been implemented in the interim, there's a whole lot more variety in shapes, sizes and styling across all brands now than ever if one cares to look.