USMCA (the NAFTA replacement; a free trade agreement between the US, Canada, and Mexico) does have some restrictions on the automotive industry in Canada and Mexico, but Mexico has been an automotive powerhouse for years now.

Mexico is already the 6th largest auto producing nation - basically the same size as Germany and South Korea. Mercedes already produces vehicles in Mexico (as does Audi, Baic Group, BMW, Stellantis, Ford, General Motors, Honda, Hyundai, Kia, Mazda, Nissan, Toyota and Volkswagen). About 70% of Mexico's vehicle production heads for the US and employs over 1M people. Mexico accounts for 23% of North American auto assembly. Mexico also imports about 50% of its auto parts from the US.

Before NAFTA, Mexico had restrictions requiring vehicles to be made domestically from domestic parts. NAFTA opened Mexico to US vehicles. Over time, Mexico's automotive industry took off assembling many US and foreign vehicles and creating lots of parts.

As of 2021, US/Canadian auto workers earned an average of around $20-21/hour. USMCA requires that 40-45% of auto workers earn a minimum of $16/hour, including all the parts manufacturing, etc. (NAFTA didn't have this wage requirement)

When you create free trade agreements, it can cut both ways. It opens Mexico to lots of US goods and services and it also means that Mexico can export to the US. At the same time, we've only seen moderate movement toward Mexican manufacturing with US/Canadian manufacturing accounting for 77% of North American manufacturing. Companies haven't just up and moved their American manufacturing to Mexico. Companies are still opening new US plants. Rivian is opening a $5B plant in Georgia (and before you say "because of the tax credits if you make EVs in the US" those also apply to countries we have a free trade agreement with like Mexico). Hyundai/Kia is opening a new plant in Georgia. Ford broke ground on a new plant in Tennessee in 2022, one of 4 new US factories. VinFast (a Vietnamese auto company) is opening a $4B plant in North Carolina. GM is spending billions on new US facilities.

So when someone says that automotive production will all be moving to Mexico because of this, it seems unlikely. Yes, Mexico will become an increasingly important part of the North American automotive industry, but we're seeing companies continue to invest in US factories - including unionized US factories. That's not to say that unions have zero impact on the planning decisions of automotive companies, but the view of the comment that you're responding to (that automotive production will simply be moved to Mexico) probably isn't going to come to pass in a clear-cut way. The US and Mexico have had a free trade agreement for 30 years now and we simply haven't seen companies run away from unions to Mexico. That's not to say that companies haven't used Mexican plants. They have. But we haven't even seen this type of thing come up in union negotiations. Mexico is producing around 30% more vehicles today than when free trade started. US production is flat, German production is down 20%, Canadian production is down 50%, Japanese production is down 25%, French down 60%, British down 40%. The US automotive industry isn't without issues, but it's doing pretty well compared to a lot of peer nations - even while Mexican imports are there.

Again, I'm not saying that it has no impact, but there's no evidence that the sky is falling. It's a political boogeyman more than a reality. It's also important to note that US vehicle production basically hasn't moved much since 1950. In fact, from 1950-1980, US production was around 8M vehicles per year. US automotive manufacturing is higher now than it was when we had more protections against cheap Mexican cars - while other high-income countries have seen declines and despite the fact that US automotive manufacturing saw no growth for 30 years when there were plenty of protections. It's not like US cars were a growth industry and then that stopped when Mexican imports happened. US auto manufacturing was a stagnating industry for decades then free trade with Mexico happened and US auto manufacturing has done better. The sky isn't falling, companies are still investing tens of billions (probably hundreds of billions combined) in new US auto manufacturing, and I don't think this vote is going to make much of a difference.