The United States is not a beacon, not a light of freedom! She is a warning, rather than an example to the world!

Lydia Maria Child (1802-1880) American abolitionist, activist, journalist, suffragist

Speech, Massachusetts Anti-Slavery Society 25th Anniversary Conference (1857)
    (Source)

On slavery in the US, two months before the Dredd Scott decision.

Almost always elided as "The United States ... is a warning, rather than example to the world."