US weapon challenges?

Dos the US wepon DLC come with its own challenges?
“Kill x number of hunters with the N9” for example?

I don’t think so. After day 4 no special task regarding the US weapon DLC was offered.

No, it does not. Only thing you’ll get with U.S. weapons DLC is three U.S. made weapons and their mag extensions. Also, you’ll get each of them in your Plundra to start you off and you can find any quality U.S. weapons + their mag extensions from machine loot pools.