South Korea's stock market just crashed hard, and this is framed as a warning that the US could be next because both markets are running on huge amounts of borrowed money betting on AI.

• South Korea's market nearly tripled in a year on AI chip stocks Samsung and SK Hynix, then dropped 25% in three weeks and wiped out hundreds of thousands of accounts.
• Millions of regular Koreans borrowed money to pile into just two stocks, so when prices fell, forced selling snowballed into a doom loop.
• US chip stocks selling off ahead of Micron's earnings triggered the Korean crash, showing how tied the two markets are to the same AI bet.
• US borrowed money in stocks just hit its highest level ever, higher than the dot-com bubble and 2008, and the real number is even bigger once leveraged funds and options are counted.
• The whole thing rests on four companies (Microsoft, Google, Amazon, Meta) spending three-quarters of a trillion dollars a year on AI, with returns on that spending already shrinking fast.

Outlook: If even one of those big companies cuts its AI spending, likely in late 2026 or 2027, the same margin-call unwind that hit Korea could hit the far more leveraged US market.