Taco Bell's five-year effort to sell its Mexican-American food in India has been a slog. For one thing, "quesadilla" roughly translates in Hindi to "how much?" Sales never took off. Initially people in the U.K. and Japan didn't cotton to the taste, and many locations there were closed.

Now, facing a saturated market for its pizza and chicken overseas, Yum Brands Inc. is nonetheless under renewed pressure to get the world to finally embrace its Mexican food. The chain has been performing well in the U.S. while Yum's KFC and Pizza Hut stores in China are facing a slowing economy and changing consumer tastes.

Faster Taco Bell expansion overseas may give Yum the boost it needs. In April Taco Bell returned to Japan, opening a single store in Tokyo, which is part of a plan announced in 2014 to open 1,300 Taco Bell locations around the world by the end of 2023. It won't necessarily be easy, say some market researchers.