The pillars of the old U.S. economy have been crumbling for decades.

The steel industry isn’t what it once was, and two of the three automakers survive only as wards of the state. IBM and GE aren’t what they used to be, and Boeing can’t seem to get its latest and greatest commercial plane, the Dreamliner, off the ground.

But there is one area in which American know-how and gumption are unrivaled, and that is in the lucrative market for cool stuff. America is still the engine of global pop culture, which drives a big part of the economy. It’s in the realm of the imagination that America excels.

“We still represent many, if not most, of the world’s most iconic brands,” said Gary Stockman, CEO of Porter Novelli, a public relations firm. “We represent imagination, innovation.”

American movies continue to pack theaters around the globe. All 20 of the worldwide top-20 grossing films so far this year come from American studios, according to Box Office Mojo. This year’s top draw, Harry Potter and the Half-Blood Prince, took in more money in foreign box offices than it did domestically—pulling in $595.5 million abroad and $291.1 million in the U.S. Now, granted, Harry Potter was created by a Brit, and the actors are all British, but an American studio, Warner Bros., released the movie.

Apple is getting ready to bring its beloved iPhone to China, where one analyst told the Wall Street Journal it could sell 2.9 million of the smartphones by 2011. The company has sold 26 million iPhones in 80 countries, though most of those sales have been right here in the U.S. Already, an estimated 1.5 million iPhones have been sold in China, even though the smartphone is not officially for sale there.

China Unicom, has signed a three-year deal to sell the iPhone in China, China Unicom announced Friday.

Harley Davidson is opening a division to sell hogs in India beginning in 2010—and in the selling, to bring the image of the open road always associated with its brand to the world’s second-most-populous country.

They’re taking iconic American brands to the world, and they’re selling them by making them part of the local scenery. As Matt Levatich, president and chief operating officer of Harley-Davidson Motor Co., said about his company’s India plans. “We believe Harley-Davidson has outstanding opportunities for continued growth around the world.”

Think Coca-Cola. Think McDonalds and Le Big Mac’s popularity in Paris even when the French were not feeling too friendly toward the U.S. Think Nike. It’s what we do. We take businesses, and maybe more importantly, the ideas behind those businesses, and we plant those ideas in the world’s imagination.

That’s certainly Harley’s plan. India is the world’s second-largest motorcycle market. But its domestic bikes lack the rumble, the roar, and the power of a Harley-Davidson. Sales there have been dominated by small, inexpensive bikes used as basic transportation.

As the Indian middle-class grows, and the country makes improvements to its roads infrastructure, Harley sees an opportunity.

“Given the rapid development of India’s economy and physical infrastructure, this is exactly the right time to bring the world’s greatest motorcycles to one of the world’s largest motorcycling nations,” Levatich said. “Our unique brand, distinctive motorcycles and strong experience in the leisure motorcycle market make us naturally suited to help lead and define the next era of motorcycling in India. We know the relevance of the Harley-Davidson brand rings true in India just as it does in other markets around the world.”

The Milwaukee, Wisconsin-based company has established a subsidiary to be located in Gurgaon, near Delhi, and headed by Managing Director Anoop Prakash. The next step, and it’s an important one for Harley, is growing the Harley brand through a network of local dealers.