a) It explains why we are in the state that we are in (because of the history of civilization; because of forces from the outside determined to defeat the nation and forces from the inside determined to weaken it);
b) It is based on the rational self (allegiance to a particular country becomes the "obvious" or rational thing to believe);
c) It legitimates certain practices on the basis of the interests of the state (e.g., tolerance of restrictive measures such as the Patriot Act);
d) It is abstract (based on the abstraction of the nation itself - an apotheosized historical contingency)
e) There is a sense of emancipation. The problems are clearly identified - insufficient belief in the collective identity of the nation, and those who serve as its symbols, usually the government. Emancipation comes through belief in the nation and devotion to its aims.
It is worth noting that nationalism is ambiguously modern (as, indeed, are all the examples given). It is possible to believe in nation without making that a modern preoccupation. It is also possible to believe in nation as an anti-modern proposition (e.g., Nazi Germany).