Why do you think the National Anthem is only
the first verse instead of the entire song?

it is because the first verse is representing america the rest of the song does to but the beginning talks the most about it

The song is offensive and could cause conflict, as we have already see the NFL. The national anthem is composed of 4 verses, one of them makes a distinct reference towards slavery.

Explanation:

Francis Scott Key wrote it as a poem, he also owned several slaves and abused his power as a lawyer by persecuting abolitionists. He referred black people as "a distinct and inferior race of people."

In the third verse of the poem Key states, "their blood was wash'd out of their foul footsteps pollution. No refugees could save their hireling slave. From the terror of a flight or gloom of the grave."