Except when the unhappy people are so used to smiling that they just force a smile because that's what's socially acceptable. Default expressions are two-faced.
Even polite smiles are still polite and show concern for the emotions of the other.
When Russians glower at me and talk in their cynical, biting tone I feel as if they don't care about me or my feelings and aren't interested in a positive emotional exchange.
Russians suck all the life out of rooms with their frowns and sarcasm.
But it's also important to note that this is an expectation of your culture — it's not as obvious to me that smiling all the time is necessarily a "happiness" thing. Surely you must be aware of the stereotypes that are held by other cultures of Americans?
The fact that you see Russians as people who suck the life out of the room, just suggests to me that you are projecting your expectations of societal norms on other societies — where they don't necessarily fit.
Reading & listening beyond the obvious expression may be more valuable than just taking it at "face value".
That said, the smile is probably more useful as a default than a glower or frown. At least it does seem to present a willingness to open dialog. People are more likely to approach someone who is smiling at them, than someone who is sending them an icy look.
Most people live very shallow, materialistic, egotistical, narcissistic lives. They also smile to seem happy, friendly, and desirable. It does not represent the real person inside.
Take what you have written: it's judgmental, borderline racist, and narcissistic.
There is little chance that you are truly enjoying life, except in the typical / selfish ways (I'm not that much different).
No one can "suck all the life out of a room." If their behavior affects you in such a way, it is only so because you require / desire perceived positivity from the rest of the world. It's like a drug / an opiate that keeps you from screaming inside.
Also, in a topic like this where we're examining differences between cultures, it's pretty implicit that we're speaking generally. If that's racist, any cultural examination is racist.