Currently the smallest cars that GM builds in various regions are all based off completely different platforms. The Opel Corsa is a completely different animal from the Chevrolet Aveo, for example. GM has been making many of their other platforms global including the Epsilon (Opel Vectra, Chevy Malibu, Pontiac G6 etc), the Zeta (Holden Commodore, Camaro, future Impala), and Delta (Opel Astra, Chevy Cobalt, next Saturn Ion).
Now the smallest GM cars are going global with the new standardized Gamma platform. With expected volumes of 1.4 million units worldwide, the potential savings are huge especially for small low margin vehicles. The 2009 Chevrolet Aveo and Opel Corsa will both be built off this new platform. Gamma variants under a variety of badges could be built in such far flung locales as Korea, China, Thailand, India, Germany, Mexico and Venezuela. Previous attempts at global platforms have been stymied by regional management, particularly in Germany and the US, demanding locally specific differences that drove up the cost and reduced commonality. New programs like Gamma and other recent platforms have been architected to allow for greater regional flexibility, while still using many common components, such as engines, transmissions and electrical systems.
[Source: Automotive News - subscription required]