Fears that Washington will tighten rules on artificial intelligence and data center construction sent the Philadelphia Semiconductor Index down 12.2% on Thursday, Reuters reported, and the selling spread to chip suppliers in Seoul and Tokyo. The Nasdaq Composite fell 5.5%, and about $3 trillion of market value was erased from S&P 500 companies in a single session.

For Asia the policy question is now a pricing question. South Korea, Japan and Taiwan supply much of the memory, testing gear and fabrication equipment that goes into U.S. AI data centers. If tougher oversight slows that construction, the order books of those suppliers are the first place it shows.

Regulation risk moves from footnote to price

Investors spent most of 2026 arguing about whether the returns on AI spending would justify its cost. This week a second worry was added: that the results of the Nov. 3 U.S. midterm elections will bring more regulatory scrutiny of AI development and of the data centers that power it. Reuters cited both fears of regulatory scrutiny and a slowdown in the AI build-out as drivers of the rout, which it called the steepest U.S. drop since the tariff-driven "Liberation Day" selloff a year and a half earlier.

The concern so far is about direction: neither report named a specific bill. The Jakarta Post noted that analysts see another cost markets may not have fully priced: rising local opposition to data center projects and the community costs they bring.

The Nasdaq had swung higher right after the vote, then reversed. As of Thursday's close it was about 12% below the record it set a month earlier, according to Reuters. Wall Street's volatility index jumped.

Michael McCarthy, chief executive for Australia and New Zealand at brokerage Moomoo, told Reuters he saw "a real shift in sentiment." Nick Ferres, chief investment officer at Vantage Point Asset Management in Singapore, said he expected "an ugly day" for semiconductor and memory shares, and that U.S. Treasuries could rally much further.

Tokyo and Seoul take the first hit

The damage in Asia began before the U.S. close. In Tokyo on Thursday, chip tester maker Advantest fell 14.7% and equipment maker Tokyo Electron lost 9.4%, according to dpa-AFX figures carried by Malay Mail. The Nikkei 225 fell 1.79% to 61,077.90, though the broader Topix rose 1.16% to 3,940.39 as Toyota Motor jumped 16.7% on a higher profit forecast. Japan's chip stocks were already under pressure earlier in the week, when the Nikkei fell 3.6% by midday after the Culture Day holiday.

Seoul fared worse. The Kospi dropped 5.28% to 5,383.80 on Thursday as foreign investors sold for a fifth straight session, dpa-AFX reported. The index is heavily weighted toward memory makers whose growth now depends on AI server demand.

The selling deepened on Friday. The Kospi fell more than 8% in early trading, triggering the exchange's circuit breaker and a 20-minute halt, The Jakarta Post reported, while the Nikkei was down about 5%. Reuters said chipmakers and data center equipment suppliers in South Korea, Taiwan and Japan looked most exposed, having already fallen on Wednesday and Thursday.

Where money went instead

Not every Asian market moved the same way. Hong Kong's Hang Seng Index rose 3.67% to 24,796.98 on Thursday, led by Alibaba and Tencent, according to dpa-AFX. Australia's S&P/ASX 200 gained 2.61% to 9,065.10, a two-month high.

Lower oil prices and easing bond yields helped those markets. Brent crude traded near $95.08 a barrel after falling almost 9% in the previous session, and gold rose nearly 2% to about $4,125 an ounce, dpa-AFX reported. Reuters said bonds were set to gain across Asia on Friday and the dollar slipped against the yen and the Swiss franc.

The split matters for regional portfolios. Earlier this week, U.S. tech results already knocked chip-heavy funds in Korea and Taiwan even as the Dow rose. The regulation angle adds a risk that earnings cannot offset: rules that slow permits or add conditions to new data centers would delay orders for memory and test equipment no matter how strong demand looks on paper.

What investors lack is detail. None of the reports cited a draft law on AI or data centers as the trigger. Until proposals appear, Asian suppliers' shares are likely to trade on guidance from their largest U.S. customers. The next marker for Seoul is whether foreign selling of Korean shares, now five sessions long, extends into a sixth.