Is a Gas Mask a necessity in the US?

i think its a bit excessive. i mean there is always a possibility of us being attacked, but hey same with everyone else in the world.
if you live somewhere like kansas, maine, north carolina, or anywhere that isnt crazy important ( D.C, virginia has langley, major cities like chicago, san francisco, etc) then i wouldnt even bother thinking about

if you do live near something important or a major city then i would still think getting gas masks are excessive, but i'd understand it if you did get one. but yea theres no way ohio is going to be the target for a chemical attack

If you need it in the future and don't have it, you are a goner.
If you never need it but have it, no problem.
Understand though, a gas mask is not something you throw in a box for a few years and expect it to work properly. You must always keep testing it and replacing parts that get dry rot. Is it possible you would need it in the states...yes. Is it probable that you would need it...no.

A gas mask will do as much good as the duct tape Homeland security suggests you seal your windows with in cause of a nuclear attack.

It depends on your location. If you live in any major city, then it is a good idea.