You may have assumed that Yum! Brands (NYSE:YUM), the operator of Kentucky Fried Chicken, Taco Bell, and Pizza Hut, is an American company. You'd be wrong.

I noticed in the company's annual report the other day that operating profit growth for its units of KFC, Taco Bell, and Pizza Hut was just 5% in the United States -- and more than 20% in China. The company already has more than 1,822 KFC units in mainland China -- versus just 784 for McDonald's (NYSE:MCD). And Yum! plans to have more than 20,000 locations in China one day, thereby generating more profits abroad than it does in the U.S.

Of course, Yum! is not alone in looking to China for big growth, and perhaps unbeknownst to you, much of your holdings' profits may be coming from there.

What's good and bad about it
There's clearly opportunity in China. Its middle class, numbering around 300 million people (according to Yum!), is about the same size as the entire U.S. population -- and it's growing.

As the investment of U.S. companies in China (and elsewhere around the world) grows, it's likely to boost many firms' earnings, serving us shareholders well. But there's a danger in it, too. China is simply not as stable as the United States. In fact, few countries are. (The United States is history's longest continuous democracy.)

If China decides to change its rules in a big way for international investment, many companies in which we're invested might suddenly find themselves in very different operating environments. This could affect sales and profits, or it could not. But the international arena is simply more uncertain than our familiar home turf. And with international revenues accounting for more than two-thirds of McDonald's revenue, roughly half for Procter & Gamble (NYSE:PG), about a third for PepsiCo (NYSE:PEP), and close to three-quarters for ExxonMobil (NYSE:XOM), you can see why any future uncertainty could have pronounced effects.

What to do
Instead of avoiding foreign investments (which provide useful diversification, not to mention great growth potential), we should keep an eye on international developments, so that we'll notice if any major economies abroad start experiencing hiccups or seizures.

That kind of international vigilance isn't something many of us would like to spend much time on, though. Fortunately, if you invest in some top-notch managed mutual funds, you'll have smart people making the tough decisions for you -- for example, which stocks to buy and when to sell. When they sense that a certain country is becoming unstable or otherwise unattractive, shrewd managers can pare back investments there. These folks can build your nest egg for you, so that your retirement can be as comfortable as possible.

One fund that might interest you is the Oakmark Global Select (OAKWX) fund, run by a respected fund company and focusing both on domestic and international stocks. The fund's top holdings recently included DaimlerChrysler (NYSE:DCX) and Dell (NASDAQ:DELL). It's a brand-new fund, though -- less than a year old -- so it doesn't sport much of a track record yet.

Finding funds
If you're looking for some outstanding mutual funds (and even some individual stocks) to invest in with an eye to retirement, let us help. Our Rule Your Retirement newsletter frequently sports some solid stock and fund recommendations and can help you design an asset-allocation plan to maximize your savings. The April issue, for example, listed dozens of top funds, many with five-year annualized returns of more than 25%.

I encourage you to try Rule Your Retirement free for 30 days. You'll have full access to all past issues, so you can read up on every recommendation and get a host of other retirement guidance as well, such as how to minimize your tax bite and how to not run out of money midway through your retirement (yikes!).

Longtime Fool contributor Selena Maranjian owns shares of Yum! Brands, McDonald's, and PepsiCo. Dell is a Motley Fool Inside Value and Stock Advisor recommendation. The Motley Fool isFools writing for Fools.