Cold cuts are also an issue, so scarce and expensive in Kenya that the $9 price of a footlong roast beef sub at a Subway in Nairobi is actually slightly higher than the cost of the same sub in many stores in the States. And that’s ignoring the fact that the United States’ per capita income is more than 40 times Kenya’s.

Mr. Bak cited the example of McDonald’s passing out potato seeds to Indian farmers years before the first McDonald’s opened in India, to make sure there would be a steady supply of perfect potatoes for McDonald’s fries.

“You can make that kind of investment if you’re going to open hundreds of stores,” Mr. Bak said. “Here, it’s much smaller, so most of the franchises are not corporate-owned.”

Still, he predicted that with population growth charts showing that almost two billion babies will be born in Africa in the next 35 years, soon enough “everyone will be here,” meaning McDonald’s, Burger King, Pizza Hut, Walmart and all the major American chains.

Fast food in Nairobi used to be chicken and chips from a local spot like McFrys or barbecue at a roadside thatched-roofed shack. To outsiders, it might seem a shame to have a part of the world so full of its own charm get sucked into the homogeneity of everywhere.

But few Kenyans seemed upset about that.

“It’s better for everybody, because it’s top quality,” said Simon Kamau, a Kenyan businessman who has lived in America.

“Popeyes, man,” his eyes glowed wistfully. “I bet people here would love that!”

Step into a Subway in Nairobi and it is as if you are leaving Kenya, or entering the new one. The glass doors are so clean you could easily knock your forehead into them, the floors are mopped spotless, the air redolent of freshly baked bread. The racks of warm chocolate chip cookies are right next to the cash register, just where they should be.