If you're not from the U.S. you have to understand the background of mendacity that flows through nearly the entire culture. That's a big part of the backdrop for fairly deep levels of distrust, whether it's of a company, one's colleague, the gov't, etc.
For example-- I was watching a political show where the question was something about global warming. One of the guests gave a reply that sounded vaguely reasonable but wasn't clear. The host tried to rephrase the question, and the same respondent again gave a suspiciously confusing reply. This caused the host to drill down on a simpler question-- did the guest believe that global warming was real and that human activity has contributed to this global warming? This time the guest answered a different question, addressing the reality of global warming but ducking the issue of causes. This went on for about 45 seconds before the host finally forced the guest to give a response that revealed the guest was in fact a climate denier. Honestly, it was like watching that scene in Blade Runner with the Voight-Kampff test, except on humans.
Being an American myself, I could immediately tell what the guest's purpose was: to sound like they agreed with the other (sensible) panelists, in order to give more credibility to a climate denial talking point that their job depends on. It's a planned strategy essentially of "denial-in-depth"-- try to sneak FUD into an otherwise good faith discussion, and if that doesn't then reveal your crude talking points for what they are.
In a weird way, the process of figuring out someone's level of earnestness makes me think of the "Sie" to "du" journey in German. Except here in the U.S., it's a slow slog of figuring out exactly how a friend spouts bullshit and under what circumstances, and then figuring out if there's enough earnestness left to become close friends.