I think mbesto's list was supposed to highlight the fact that a large number of China's top companies are state owned.

The US economy is 70% larger than China's, it should have far larger companies. The US also has vastly larger multi-nationals, that have between 30 years and a century of lead time in competing for / capturing international markets - once again, it makes perfect sense that the US should have more mega-corps. The US also has a vastly more evolved economy, including an extremely large services segment (which China is currently attempting to clone as their manufacturing continues to contract). As China develops the services side of its economy, you'll see dramatic consolidation in the number of mom & pop shops, leading to large service companies (which is why KFC is so massive in China; if this were 20 or 30 years later, China's service sector would have already produced it domestically at scale).