That would be an extremely difficult mod to make SnSKiller, and probably a controversial one as well. I can see how maybe some buildings from the Khergit towns in Native could be used to look like bits of Afghanistan, but the rest of the game would have to be built from scratch.
Plus, you'd need loads of guns... which can be done, but is quite tough... and loads of costumes... and helicopters, APCs, etc...
Helicopters have neverr been done in M&B.
I don't want to put you off the idea just in case you're serious enough about it to do all the work that would be needed, but it'd be a hell of a struggle.
If you just want an Afghanistan mod with NATO/UN troops then there's a brilliant old one for Operation Flashpoint, and a newer one for Armed Assault. In M&B it would be near impossible to recreate that kind of warfare, though, in my opinion.