There's no singular thing as American culture, obviously. There
are several variants depending on where you go. Some places
inherently have more conservative values, some places are politer,
some places are more "liberated".
That said, an overarching umbrella representing the American
culture would likely involve the following attributes: liberty,
individualism, autonomy, ideas/thoughts/rationale over
sensitivities/feelings/emotions, consumerism.
Liberty: One of the three "inalienable rights" mentioned in the
Declaration of Independence, and possibly the only indisputable
item on this list. It is the freedom to not have to answer to a
tyrannical entity, not being dictated what to do, and instead the
freedom to pursue what you choose to of your own volition, being
free to face the consequences.
Individualism: Elevation of the self over community; personal
freedoms take priorities over community needs.
Matriarchies/patriarchies are muted compared to other cultures. You
work for yourself, your children earn their keep. Even if your
marriage is not working out, your sanity and needs are
paramount.
Autonomy: The idea of being in self-control of your own future.
You're personally free to do what you please, but you also
enjoy/suffer the consequences of your own actions. If there's
anyone to blame for the state of your own life, it's yourself and
none other. The system exists to support your autonomous
functioning in the best way possible.
Ideas over sensitivities: Most of the time, the best idea wins.
Of course, politics cannot be completely eliminated, but
hierarchical relationships are suppressed in the professional
atmosphere. And everyone is expected to question and root out bad
ideas, regardless of whom it may offend. You have the right to
offend as well as the right to (not) take offense. This quality is
one of the drivers of innovation as understood in the American
culture.
Consumerism: The culture largely promotes consumerism -
although this may seem negative to an outsider, it is the driver of
"producerism" too. i.e. innovation. Everything is geared around
having more money in circulation in the economy. Hoarding money is
de-emphasized and considered to be contrarian to the economic
principle of capitalism.
With only minor variation in these core principles, even
mainstream Americans come in all shapes and sizes, with hugely
differing beliefs. But quintessentially, it is these core values
that forms the glue that binds Americans together.
In general American culture promotes real diversity, not the
cultural war that is so often called diversity by the Left. Want to
eat a style of food go for it, even if your ethnicity is not the
same as the food. Follow your taste buds not your heritage. Listen
to music that moves you not music prescribed too you by somebody
else. Most other cultures in the world have strong social pressure
to act, dress, speak and act in certain ways.