Cultural stereotypes are a dangerous and corrosive thing. They teach us that Poles are a tribe of thieving simpletons; or that Americans are arrogant, violent, and obese. And that's just the ethnicities that get off easy: the perception of blacks, Muslims, or European Jews can be far more vicious, often serving a pretext for violent hate crime.
At the same time, there is no denying that certain unique archetypes are etched into the fabric of every society. I'd also posit that when cultures come into contact with each other, there is an uncanny valley effect at play: the more similar the nations are, the easier it is for travelers to instinctively pick up the subtle variations - and to misread them as the personality quirks of the people they interact with.
For Poles who settle in the United States, the most striking contrast of this sort must be the persistence with which Americans want to engage in oddly personal small talk: you will be always greeted with "how are you?", be it by the cashier at a grocery store, by your mailman, by the park ranger met at a trail, or by the waiter serving your food at a restaurant. The social expectation is to share short pleasantries or announce a brief piece of good news. But if your answer is overly specific or focuses on a negative event, you may be given quizzical looks and the conversation will stall.
To many of my compatriots, the exchange - lacking any apparent purpose - feels uncomfortable and insincere. I try not to look at it in a cynical way: the upbeat chit-chat, repeated over and over again, can probably make your day a bit better and a tad more fun. This constrained form of communication also provides something to build on the next time you see that person, even if every individual interaction is necessarily non-committal and brief.
Another explanation for the forced positivity may have to do with the pervasive can-do spirit at the core of the American culture. The national ethos of self-determination and unconstrained social mobility flies in the face of the daily struggles of disadvantaged citizens - but it remains a fundamental part of the cultural identity of the United States. The American Dream manifests itself everywhere, from the country songs of the Midwest to the high-tech entrepreneurship of the Silicon Valley. Your friends, coworkers, neighbors, and even complete strangers are there to support you when true calamity strikes - but dwelling on everyday mishaps is almost universally seen as a weakness that one needs to overcome in order to succeed in life.
In this regard, the Polish culture is strikingly different. After hundreds of years of political repression and foreign control, Poles have developed a colorful tradition of sarcastic humor and idle lamentation. This coping mechanism functions to this day: to a Pole, being asked about your day is seen as an invitation to air all the petty grievances; you wouldn't expect a friend to smile, exclaim "I'm doing great!", and move on. Complaining about politics or work is how you build rapport with your peers. In fact, being overly upbeat or talking about professional success or accomplishment is likely to be met with suspicion or scorn. If you're a successful entrepreneur, you will probably open by complaining about your dealings with the Polish equivalent of the IRS.
In many ways, the Polish approach to chit-chat is more genuine and less rigid. At the same time, I feel that the negativity comes at a price; meeting a cranky clerk at a store sets the tone for the remainder of your day. The constant pessimism can also dampen some altruistic instincts: relatively few people in Poland get engaged in their communities or dedicate themselves to other forms of civic service. It is more accepted to just complain about the ways things are.
Interestingly, in the United States, the boundaries that govern the conversations with complete strangers also extend into the workplace. When interacting with casual acquaintances, sarcasm is seen as jarring, while petty grumbling is perceived as an off-putting and unproductive personality trait. Off-color humor, widely tolerated in Poland, is usually inappropriate in white collar environments; doubly so if it comes at the expense of women, immigrants, or other disadvantaged social groups.
Some Europeans characterize the workplace etiquette in the US as political correctness run amok. There are situations where political correctness can stifle free speech, but I don't think it's one of them; for most part, not hearing political rants or jokes about blondes or Jews just makes the world a bit better, even if the comments are uttered with no ill intent. Violating these rules will not necessarily get you in trouble, but in a culturally diverse society, it can make it harder to find new friends.