Circuit breakers are now more common. The US has them at whole-market level and individual stock level. Somewhat like an API rate limit, there are tiered penalties - the bigger the intraday drop the longer the time-out period. In the worst case the market will be shut down for the day to cool off. This is one reason you occasionally hear about the exchange ‘stopping trading’ of a security.
More important is why they do it: it's a chance for the market to pause and rationally assess automated trades. The reason we're seeing it more often is because it's a reaction to stuff like "flash crashes", which weren't a thing (as much of a thing, anyway) before bots took over the market.
Of course, journalism remains trapped in a death cycle of click-chasing stupidity. This means that the triggering of the mechanism itself has now become a source of hype to propagate the panic ("OMGOMGOMG the market fell so fast that it tripped the circuit breakers!! Panic! Flee! Run away!"), so it's less clear that the mechanism is a net good.
The exchange is open now anyway, so you can look how it's going.