My bad, I thought you (and @EinsteinsHund) meant saying “good health”, not literally saying “Gesundheit”. Yes, I have heard people in the US use the German phrase. Sorry for the confusion.
The origin of the saying was something along the lines of Xian fears that the soul leaves the body during the sneeze, so god was quickly invoked to put it back. And that is idiotic.
I agree we should not be treating sneezes any differently that coughs or burps. They need no acknowledgement from family, friends, or strangers unless the attack is getting severe enough to be health-threatening.
And then what they need is physical assistance or a call to the emergency medical services. Not a tiresome invocation to a nonexistent god rather few humans believe in.
FWIW I only ever hear it from Black cashiers, and, no, it doesn’t ever bother me. However hearing ‘Bless you!’ after a sneeze is annoying to my ears.
I first learned that English speaking people sometimes are used to the German phrase “Gesundheit” when the company I worked for did a contract software project with a Canadian company. For the deployment, the Canadian developer came over to Germany and we worked together for a few weeks. At one time, he sneezed, and someone said “Gesundheit!”. I began to translate and explain to him, but he said "Oh, it’s ok, I know what it means, we often use to say it in Canada, too ".
I’m another Gesundheiter in a bless-you world.
I say Gesundheit when others sneeze. Always have, reflex action now. I grew up in Chicago, where it was pretty common (plus which I’m partly of German descent). Seems less common in NY Hudson Valley, where I live now and where “bless you “ is much more frequent.
To the OP, I hardly ever hear “ have a blessed day” and wouldn’t bother me at all if I did.
Gesundheit here as well.
I notice, but pretty much ignore “blessings” - other than to think mildly negatively about someone I otherwise would have had a neutral opinion of. And when panhandlers write “God bless you” on their signs, that effectively guarantees that I will not give them anything. But they probably don’t need my contribution since their lord will provide…. 
Some one sneezes we say “Scat Cat”
I hear the “have a blessed day” thing from cashiers/clerks.
And I hate it.
I wanna say…”I refuse’
But I never have. I silently seethe.
It’s akin to “bless your heart” that’s so hated.
I don’t get the blessed day very often, but do get plenty of bless yous after sneezing. I’m partial to salud myself (followed by dinero and amor for multiple sneezes).
I’m atheist and am not bothered in the slightest by any of them. I think most people who say it are just giving a stock verbal response, just like when people ask “how are you” they’re not really wanting to know how you are.
I’ve said Gesundheit all my life, though I didn’t know exactly what it meant until I was in my teens.
To be clear, the word “Gesundheit” just straightly means “health”. But spoken as a reaction to a sneeze, it implies the meaning “(Good) health to you”, as I freely translated it.
Yeah, I know, but as a little kid, I didn’t.
When I get this, I just respond “You have a great one!”. I do want them to have a great day, but as an atheist it would be weird for me to respond with “blessed”.
So what? What tiny fraction of people who use the expression are aware of that or are thinking that? Words have meaning based on the way they are used, not some ancient etymology.
As for the OP, not here (San Francisco) among the people I interact with. It would mildly annoy me, as a way to sneak in a religious reference without any possible recourse on my part. It might chip a couple of points away from my good mood. But that’s all.
This exactly. I don’t really hear it much here in NYC but it doesn’t bother me at all. It’s just someone being nice.
Probably around the same as the tiny fraction of people who say “have a blessed day” specifically to rub it in the face of atheists rather than because in their mind “good” and “blessed” are basically synonyms.
My Granny was known to use “blessed” as a mild expletive.
As in “That bless-ed hose leaks”
I disagree to a certain extent. While it is indeed probably unlikely that a person saying “Have a blessed day” is trying to rub it in the face of atheists, it is still sufficiently non-standard that I think the people saying it have an agenda (even if it is a mild one).
They could just as easily say “Have a nice day” or “Have a good day.” The fact they they say something with religious overtones is intentional, IMHO.
Which is not to say it is malicious, by any means. It could be anything from mere religious enthusiasm to a “holier than thou” attitude. Whether they realize it or not, though, they are irritating many of the people they say it to, as evinced by many of the responses in this thread.
At a minimum, they are guilty of assuming that everyone will appreciate being asked to have a blessed day, or not caring.
Pretty much this.
‘Have a blessed day’ is just a more glurgy variant on a stock courtesy and since it is someone trying to be polite and friendly I don’t have much issue with it. Yeah, it implies a shared religious faith that’s not applicable to me and the first time I heard it I found it slightly startling. But I’m not a militant atheist, but something a little closer to an apathetist - I just don’t give a shit.
I don’t really care if someone assumes I’m religious. I’ll correct them if it’s relevant or they ask, but otherwise…meh.
Granny was evidently too genteel to say “damned”. 