President Trump ordered General Motors to make desperrately needed ventilators.

It is very complicated, an expensive piece of equipment.

I would say more so than a car.

so 是替代词，替代前文说的某个词语 complicated。say 后面是个省略了 it is 的宾语从句。more so =  It is more complicated

I would say it is more complicated than a car.

【翻译】

特朗普总统下令通用汽车制造急需的通风设备。

它非常复杂，是一件昂贵的设备。

我要说，它比一辆车更复杂。