Pride in personal achievements has a catch: it's only available to those who actually did achieve something. Those who did not still have a desire for pride and "group pride" (be it national, ethnic, religious, supportership of some sports team or even just membership in some specific profession) fills that gap.
As much as i despise patriotic displays, i still think they can offer great value as a lesser evil when even more dangerous group pride identities (e.g. religious or ethnic radicalization) are just waiting to fill the gap for those in need. Not only the american, but also the french or british group identities are much more accessible than for example german (much of national identity defined by difficult relationship with history, newcomers don't share that heritage) or belgian (much of national identity defined by being of either flemish or wallonian ethnicity, newcomers are neither).
As much as i despise patriotic displays, i still think they can offer great value as a lesser evil when even more dangerous group pride identities (e.g. religious or ethnic radicalization) are just waiting to fill the gap for those in need. Not only the american, but also the french or british group identities are much more accessible than for example german (much of national identity defined by difficult relationship with history, newcomers don't share that heritage) or belgian (much of national identity defined by being of either flemish or wallonian ethnicity, newcomers are neither).