Americans are conservatives by nature, they hardly adapt to innovations, but if they accept them, they rarely abandon their beliefs.
For example, they openly discuss sex issues and do not consider it reprehensible that teenagers start having sex at 14-15 years old. But at the same time, the vast majority of residents of this country have a negative attitude to smoking and will certainly make a remark to a person if they see him with a cigarette on the street.
In general, Americans are not distinguished by good manners, but they consider it their duty to smile even to strangers. And their greeting is invariably accompanied by a question about how a person is doing. This is a visible part of the politeness that many US citizens lack so much. But do not delude yourself and think that a person is really interested in what is happening in your life. A concise answer that everything is fine with you will completely satisfy them. And they are ready to give friendly participation and attention only to really close people, but relatives and sex partners are not always among them.