Agreed,
Very little new construction items come from China.
Concrete is local, lumber used in California mostly comes from the US and Canada. THERE IS NO LUMBER COMING INTO THE US FROM CHINA. OSB board comes from the US & Canada. Windows and doors and almost all millwork comes from the US.
The only items that may come from China are: lights, faucets and cheap bamboo flooring.
Most construction materials have a much larger percentage of freight cost in their transportation to their final destination. Therefore, it is not typical to ship them half way around the world like an I phone. Also, most construction materials are commodities. There is a much lower profit margin on them. FYI, most framing lumber is only 15-25%.