Just like
@Eatmore Mudd said, the US-spec 2021+ is basically a Euro 4 but with diff lights and some stickers on the frame. We def has some old wonky lighting requirements over here, but thankfully emissions requirements for motorcycles are more lax here! It's also quite possible that some wiring colors are different - especially in the headlight area - but I'm not 100% on this. Regardless it's easy to parse once taken apart!
My 2022 US/Cali emissions-spec isn't listed at Hitchcock's, but 2021 Euro 4 parts work just fine for the engine so far. Things like their rear rack might have issues with US-spec taillight and require mods. Upgrading to LED turn signals on US-spec often requires a flasher modification, too.
That is for BS4, all 2021+ Himalayans are BS6, whether they are '21 Euro-spec 4, '21-'22 US-spec, or '22 Euro 5.