us politics thread is the opposite of an echo chamber, it's constantly plagued by infighting and arguments to the point of shitflinging and flamewars between various (groups of) users.
doomers vs optimists, nazis vs jews, conspiratards vs reasonable people, zoomers vs millennials vs Xers and boomers, interventionists vs isolationists, the exact topics change over time but whenever you open the thread it's virtually guaranteed that you'll find yourself in the middle of some slapfight between raging autists.
the three biggest echo chambers on the site are probably the ukraine war thread (russian side), the other ukraine war thread (ukrainian side) and the man hate thread.
all three of these were explicitly created/endorsed by null to serve as echo chambers for their respective audience, and jannies enforce this by keeping dissenters out, reddit mod style.