Regarding the use of tactical nuclear weapons as killstreaks:
from what I can tell the tactical nuke immediately ends the game when deployed. I don't think any other killstreak works this way, though I'm not a COD expert. That to me signifies a certain severity lacking from other killstreak rewards; it's more than just a killing device. Insofar as COD multiplayer has any ability to express any overt perspective on nuclear weapons, it seems to say "this will fuck you up more than everything else in the game," which is crude but at least vaguely accurate.
So while I think the idea of having a tactical nuke as a killstreak is ludicrous, I don't immediately think it's terrible in the same way White Phosphorus is. Setting aside all the other differences between the two--that it's probably easier for a random combatant to get their hands on WP than a nuke, and that nuclear weapons are geopolitically radioactive on a different scale--COD itself seems to respect how terrible nuclear weapons are at a game mechanics level, in a way that's lacking from its depiction of WP.