> only some stock exchanges in the world have circuit breakers
Most of the US ones do. Here's a list of recent NYSE and NASDAQ trading halts.[1] The London Stock Exchange has trading halts. Euronext has circuit breakers that trip on 8% - 10% changes. [2] The Tokyo stock exchange has trading halts, but doesn't use them often.[3] China's stock exchanges use trading halts too much.[4].
That covers the major markets. Who doesn't have some system to stop trading during big price swings?