The shock waves of Europe's debt crisis will take a toll on corporate America, particularly sellers of cars, consumer products and basic materials that generate significant revenue on the continent.

The crisis that this week claimed the heads of the Greek and Italian governments is threatening to throw Europe into recession, and has U.S. companies from General Motors Co to Emerson Electric Co scrambling to find ways to reduce their risk.

GM, the No. 1 U.S. automaker, which gets about 17 percent of sales in Europe, on Wednesday warned that it no longer expects to break even in the region this year, with Chief Executive Dan Akerson blaming Europe's economic morass.

Industrial conglomerate Emerson, which generates about 20 percent of its sales in Europe, plans to focus all of its 2012 restructuring efforts on the continent.

Europe is definitely going to be a problem, Emerson CEO David Farr told a conference on Wednesday. I expect Europe next year to be very challenging for us. But I expect them to resolve this and start dealing with their issues long term.

U.S. stocks tumbled on Wednesday and Italy's borrowing costs rose to a level viewed as unsustainable, prompting German Chancellor Angela Merkel to warn that deep structural reforms were needed for the euro zone. Unlike Greece, Italy's economy is seen as too large for the European Union or International Monetary Fund to bail out.

The crisis could push Europe into a mild recession and hit demand for everything from Big Macs to corporate computer servers, said Peter Sorrentino, senior vice president and portfolio manager at Huntington Asset Advisors in Cincinnati.

It will impact a lot of the major U.S. exporters, split out between technology and the consumer side. The McDonald's of the world are going to feel this, he said.

You might see some order-book erosion, literally across the board, from GE to Hewlett-Packard and IBM as well. This is big enough that it could affect everyone.

MANY SECTORS HIT

GE and McDonald's are among 30 companies in the Standard & Poor's 500 index <.SPX> that Citigroup called out for having both large sales in Europe, the Middle East and Africa and high debt-to-capital ratios. GE shares are down 13.6 percent this year, while McDonald's has gained nearly 21 percent. The S&P is down 1.9 percent on the year.

The industries most dependent on European sales include automobile and components companies, which generated almost 28 percent of their sales in the region, according to Citigroup chief equity strategist Tobias Levkovich. Food, beverage and tobacco companies had the next-highest EMEA exposure with 22 percent, followed by basic materials with 20 percent.

He also suggested investors should pay special attention to companies with both heavy exposure to Europe and debt-to-capital ratios in excess of 35 percent, describing those companies as potentially looking risky.

Two names that topped that list were the foreign affiliates of well-known U.S. brands: Coca-Cola Enterprises Inc and cigarette maker Philip Morris International Inc

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But the list also includes more geographically balanced companies, including glass container manufacturer Owens-Illinois Inc , McDonald's, insurance company Aon Corp , money manager Invesco Ltd and Dow Chemical Co , all of which generate at least 34 percent of their sales in the EMEA region.

It should be obvious to almost anyone that the tight fiscal programs needed to address large deficits will cause drags on European economic trends, Levkovich wrote in a note to clients.

Those concerns are not reflected in Wall Street profit forecasts. Analysts have lowered their next-quarter earnings estimates for the 30 companies highlighted by Citigroup for their European exposure by 0.4 percent over the past 30 days, less than the 2.3 percent decline in estimates for the Standard & Poor's 500 index as a whole, according to Thomson Reuters StarMine data.

DEMAND SEEN FADING

Rockwell Automation Inc , a maker of systems to help factories run more smoothly, warned investors on Tuesday that European companies' capital spending may decline next year.

The outlook there is certainly slowing, said CEO Keith Nosbusch. We know that European OEM machine makers will have a slower growth than they did in 2011 ... They feel good about the next quarter; but I think as we roll into calendar 2012, they have less visibility.

In addition to hurting European demand for U.S. goods, the crisis in the euro zone had been pushing down the value of its currency, which on Wednesday hit a one-month low against the dollar, trading below $1.36.

That could hurt not only U.S. companies' exports to Europe but even to still-growing economies in Asia. A weaker euro, for instance, could make an electric turbine made by Germany's Siemens AG more cost competitive in China than one made by GE, one investor noted.

That's probably the biggest risk, because on a relative basis, our products have been cheaper, said Peter Klein, senior portfolio manager at Fifth Third Asset Management in Cleveland, Ohio. If (the euro) goes down to $1.30 it's probably not a big deal, but if the euro goes to a buck, or even $1.05, that could have a real big impact on domestic U.S. companies selling into Europe.

(Reporting by Scott Malone in Boston, additional reporting by Nick Zieminski in New York and Ben Klayman in Detroit; Editing by Phil Berlowitz)