Mercy
Here's 5 :
https://www.google.com/search?q=a+song+that+is+about+federalism&rlz=1C1CHBF_enCA814CA814&oq=a+song+that+is+about+federalism&aqs=chrome..69i57j69i64j69i60&sourceid=chrome&ie=UTF-8
Precisely
How about, "Deutschland über Alles"? There may be other songs celebrating geographic - national unity.
If that doesn't meet your needs, how about, "The Battle Hymn of the Republic," which Julia Ward Howe wrote to celebrate the U.S. armies' re-establishment of "Federal" control over the seceeded states?
Bruce
People write songs about love, and sadness, and happiness, and dead skunks in the middle of the road, but not about federalism.