What happened to the adjectives?
Came across this headline tonight on a South Carolina paper's Web page, which set me to wondering again what's happened to the adjectives:

GOP Congress candidates spar over the issues

Whatever happened to using congressional as the adjective? They may be candidates for Congress, but they are congressional candidates, it seems to me.
And I keep seeing Iraq government. What happened to Iraqi, the adjective form listed in my dictionary?
I keep seeing other, similar constructions.
Now, I know the use of the noun as descriptive is highly acceptable (Canada goose). And it's the Democrat-controlled legislature. But it seems to me it can be overdone. Iraq government kind of works, but "GOP Congress candidates" especially grates the ear.

Or did I miss a language train as it came through?