Belial,

If one may reasonable refer to "French culture", "German culture", or "Italian culture", then yes, one can indeed say the American culture.

In general, if there exists a set of shared behaviors, or if there exists a perception of a set of shared behaviors, and if those behaviors are - correctly or incorrectly - also generally associated with a nation, then those behaviors can be referred to as being part of that nation's culture.

For example, "guns" and "America" are very commonly closely associated among Europeans.

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Eudaimonia