I think your perspective is biasing you. The US has a massive number of small and medium companies. For example small part machining there are dozens per city

I think your perspective is biasing you. The US has a massive number of small and medium companies. For example small part machining there are dozens per city. 43% of US GDP is small and medium size business. That’s effectively 50% of China’s entire GDP. Sure China has more, but it also has 4x the population and an economy more focused on labor intensive industry.