They were referencing the US far-right's desire to recreate the failed slave state known as the Confederate States of America (CSA, aka The Confederacy). The CSA was formed in Feb 8, 1861 by seven Southern US states (Alabama, Florida, Georgia, Louisiana, Mississippi, Tennessee, and Texas; South Carolina declared secession in Dec 1860; Arkansas, North Carolina, and Virginia joined by mid-1861, making the number eleven) when their goverments declared secession from the US, an action not recogized as legal under US law.

The principal reasons given by the states that found it important enough to document were the preservation and expansion of chattle slavery of those of African descent and enforcing white supremacy (this is the "states' right" that US conservatives refer to). The white supremacists were concerned about the potential abolition of slavery, the ban of slavery in new provinces, and freestates' refusal to enforce runaway slave laws aft civil war when Confederates attacked Fort Sumter, a US Army fort off the coast of South Carolina.

The CSA was marred not just by a particularly brutal form of slavery but also great wealth disparity and a severe lack of industrial capacity, due to its agrarian, plantation-slavery economy, run by its slaveowner aristocracy. Their military thus lacked domestic arms manufacturing capacity. This resulted in having to rely upon imported arms that quickly saw problems due to naval blockades, and suffered from a lack of professional soldiers and officers.

On March 18th, 1865, the CSA's government adjourned for the last time, dissolving officially by its president on May 5th of that year, 5 days before his capture while attempting to in womens' clothing (actually a thing - TIL). The span of its existence (4.25 years) is shorter than the airing of the creepy American child beauty pageant reality TV show "Toddlers & Tiaras" (4.8 years).

tl;dr - "The Confederacy" is referring to the failed slave state that fucked around and found out.