Coca-Cola's (NYSE:KO) international business is bubbling over, but recent results reveal that the beverage giant continues to battle domestic headwinds.

Fourth-quarter net revenue came in at $7.51 billion, up 5% versus the year-ago period. For all of 2009, the maker of such popular brands as Coca-Cola Zero and Powerade saw revenue slip 3%, to $31.1 billion.

Quarterly earnings per share shot up a whopping 53% on a reported basis, hitting $0.66. Exclude restructuring charges in the year-ago period, however, and shareholders are left with a mere 3% gain.

On the year, reported EPS of $2.93 was up 18%. Nice, but when we toss out special items in both years, EPS falls by what seems to be the magic number -- 3%.

Confused yet? With large, complex companies such as Coca-Cola, it can be best to head straight for cash flow, which can provide a clearer picture of business fundamentals. Here, 2009 operating cash flow set a company record, rising 8% to $8.2 billion.

We also have another handy metric at our disposal -- volume. For the quarter, both companywide and international volumes improved meaningfully from the somewhat disappointing results posted in Q3. However, the sequential improvement isn't any mathematical sleight of hand; business really has strengthened from the prior year.

Ah, but if only the improvement were uniform.

While quarterly international volumes raced ahead by 6% -- with China and India both posting massive double-digit gains -- North American volumes slumped 1%. Sure, the U.S. consumer is shifting away from carbonated beverages in general, but management also cited a weak U.S. food-service environment. Need evidence? How about Burger King's (NYSE:BKC) sluggish U.S. sales? Or the domestic headwinds eating away at Yum! Brands (NYSE:YUM) and, to a lesser extent, even McDonald's (NYSE:MCD)?

For Coca-Cola, such dynamics are hardly a pint-sized problem. North America represented nearly 21% of the company's 2009 operating income.

In my estimation, the future of U.S. carbonated beverage sales is largely out of Coca-Cola's hands. There is, however, a bright spot in the company's still beverages category, which includes such brands as Simply, Odwalla, and Minute Maid. U.S. volume held pat for the quarter, and future prospects are encouraging.

On a comparative basis, it'll be telling to see whether PepsiCo (NYSE:PEP) can outdo Coca-Cola's North American performance when it reports later this week. Meanwhile, those who strongly believe in the future of the U.S. soda business will likely get more fizz for their buck by sticking with shares of Dr Pepper Snapple Group (NYSE:DPS) or Hansen Natural (NASDAQ:HANS).

Which company will have the final toast? I don't know, but our drinks will likely be warm and flat by the time we find out.

Is Coke still the pause that refreshes in your portfolio? Or do you think the soft-drink giant has lost its fizz for good? Share your opinions in the comments box below.

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Coca-Cola is a Motley Fool Inside Value selection. Coca-Cola and PepsiCo are Income Investor recommendations. Hansen Natural is a Rule Breakers selection. Try any of our Foolish newsletter services free for 30 days.

Fool contributor Mike Pienciak holds no financial interest in any company mentioned in this article. The Fool has a disclosure policy.