Think iPhone fever has peaked in the U.S.? While the iPhone commands 23% of US smartphone market share according to Nielsen's recent survey, in Japan the number is closer to 72%. The iPhone might be a smash hit in America, but in other countries where Apple (Nasdaq: AAPL) has pursued a multicarrier strategy, its numbers are even more staggering.

Huge growth across the world
Exactly how much of a success is the iPhone abroad? Thanks to a new report from Gartner and Morgan Keenan, we have some answers. Let's look at Apple's mobile market share across the world. Remember, mobile market share takes into account all phone sales, not just smartphones. That'll make Apple's share smaller than the 23% figure quoted above.

In Canada, where five different carriers sell the iPhone, Apple's share of the mobile market is around 12.4%. In France, where France Telecom's (NYSE: FTE) Orange and two other carriers sell the iPhone, its mobile market share reaches 11.6%. In the United Kingdom, where six carriers sell the iPhone, Apple commands 10% of the market

In contrast, Apple's mobile market share  in the U.S. is just 6.5%.

America, a lost opportunity
What's the major difference here? The number of carriers selling the phone! I've said it before: Apple's blowing a monumental opportunity by sticking with AT&T (NYSE: T) as the sole U.S. distributor of the iPhone.

Just look at Google's (Nasdaq: GOOG) Android as proof. In April, AdMob released a survey showing that Apple slightly edged Google in unique devices in the U.S. However, internationally, the iPhone had a staggering lead over Android devices: 16.7 million iPhones, versus only 2.9 million Androids being used abroad.

In the fast-moving world of smartphones, stats from April are now antiquated. For example, Google's Android has at least doubled its sales pace since that time. In April, Google was activating less than 100,000 Androids per day; today, the figure stands at more than 200,000! However, the stat does illustrate how effective Apple's multicarrier strategy has been. Simply put, Google hasn't gained nearly the momentum abroad that it has in the U.S.

There are a number of factors in play here -- predominantly that major U.S. carriers such as Sprint (NYSE: S) and Verizon (NYSE: VZ) have had incentives to promote Android offerings. In other countries, major carriers have all had the iPhone, and had little need to aggressively promote Android phones. As recent studies have shown, most users prefer the iPhone; they're just backfilling to Android offerings because it's the best available solution.

Opportunity's calling
I realize that the U.S. is a different market. European countries all have similar standards that make distributing the iPhone to each carrier easier. In America, AT&T has a vastly different network from Verizon and Sprint. Still, Apple's leaving large amounts of money on the table by not expanding the iPhone to each major U.S. carrier. Android applications have soared from about 40,000 in early April to 100,000 today. The longer Apple waits to expand beyond AT&T in the U.S., the more time it gives its largest competitor to create a platform on par with its own.

America's not only the most lucrative smartphone market in the world, but also a base for the exploding growth of Android apps, which make the platform more enjoyable for users. For Apple, this is a huge problem that can be easily remedied.

You know what to do, Steve Jobs. Fix it quickly.

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Eric Bleeker owns shares of no companies listed above. Sprint Nextel is a Motley Fool Inside Value recommendation. Google is a Motley Fool Rule Breakers pick. Apple is a Motley Fool Stock Advisor recommendation. France Telecom is a Motley Fool Income Investor selection. The Fool owns shares of Google. Try any of our Foolish newsletter services free for 30 days. The Motley Fool has a disclosure policy.