A church has a doctrine to transmit in time. An association has statutes, to ensure organisational continuity. Nations, however, have a culture. It may seem simplistic, but it is possible to define culture on the basis of this. True, a minimal definition, but it does emphasise the distinction between general social activity and culture.
Nationalists say that it is.
They say any nation state must have a culture. However, this is circular reasoning. If there is no transgenerational entity, no culture is needed. The world does not end because of this. If there is no Germany, no German culture is necessary.