I find Germans have an easier time replying to things very frankly and without garnishment or humor. I can ask a German, "How are you?", and he may reply with "I'm fine" and it can be taken at face value.

Americans tend to be more, I don't know, conflict avoidant in their replies? There's more expectation of subtext, of irony, and it's not as typical to take "I'm fine" at face value.

"Can't complain" is another good one. It's often heard as, "I can't complain [because nobody would listen anyway]". Tone is important, as is environmental context. Blue collar workers at the site say this, yeah their day is going to shit. Your buddy says it over drinks, maybe he's having a neutral, normal time of life, or maybe his life is going to shit and he's giving the ironic answer to avoid diving into his real issues, while still communicating that things are not perfect.

Last week I was asked how my day was. It had been a perfectly normal, decent day, good time at work, beautiful weather, and my reply was "Life's a peach". I got back, "That bad, huh?" Yeah, the American habit of taking genuine expression and searching for a darkness under it can be tiring sometimes.