In 2019, California Assembly Bill 5 was passed regulating the use of independent truckers (Newsom's hand job to the unions). This is probably one of the biggest factors affecting the supply chain. Additionally, close to 40% (if I'm not mistaken) of the country's goods flow through CA and another factor which greatly impacts truckers is the fact that trucks older than 2011 are not allowed in CA.
You left out the part where trucking companies won't buy new trucks because California outlawed them starting 2035. There are no interstate electric trucks invented that are capable of pulling 80,000 pounds any distance without massive down time. The Democrats are great at destroying jobs. Too bad all the west coast states are bat shit liberal. They could steal the shipping industry coming from China heading to California. The California regulation is going to cause severe economic problems across the country.
1. No independent truckers allowed. Only Union endorsed companies.
2. No trucks can be used older than 2011
3. Trucking companies don't want to buy new trucks knowing they will be outlawed by 2035 in California. Interstate tractors start at around $140,000 for base models.
4. No feasible electric tractor trailer exists that can get goods thousands of miles in a reasonable time.