It's human nature to (1) distrust authority, (2) assume that authority is generally more nannying and risk-averse than you yourself are, and (3) want explanations consistent with your understanding of how the world works.
Human nature would like to disagree with you about the nature of human nature.
;)
I bet a dollar that the environment - nurture, as opposed to nature - will have a huge impact on a persons attitudes and beliefs and behavior towards authority.
Imho vast claims about human nature should be backed up with some scientific or well-sourced evidence :).
I wonder about the second point. Is it human nature or a learned reaction we have because in our lives we experience authority as overly- cautious? First our parents, then our teachers, then the government (perhaps less so, depending where we live) are constantly telling us not to do things because they're dangerous even when odds of injury are relatively low.
I don't think it's just an American thing.