Nissan, Toyota, Honda and MINI (BMW) all have major plants in the UK and Brexit is now a big risk to them.
According to whom? The UK made cars before Brexit for the EU market, and the US and Canada engage in trade without an "AU" American Union.
I can't see any foreign company wanting to break into the US market at present given the, shall we say, unstable nature of the tariff situation.
If you insist on being divorced from reality, then that's certainly your choice, but I think you're letting your politics blind you from real world numbers. Manufacturers were leaving the US at a rapid pace, especially investing heavily in Mexico for tax savings to sell in the US market, until the big threat of tariffs.
This has almost completely ended all future investment in Mexican plants, and we've already seen massive expansions in the US as well, because the market will not tolerate uncertainty, and there is certainty that a US plant ensures reduced risks. Invest in Mexico or the EU and maybe get hit with a 25% tariff in the first or second largest vehicle market in the world, or invest in the US and have zero risk of this... its a no-brainer.
"Germany, the United Kingdom, France and Japan are the leading contributors to automotive FDI in the United States. Many large automakers have committed to increasing their investments in this country, as seen through the actions of companies such as Toyota and BMW, which pledged $10B and $600M, respectively, to their U.S. facilities over the next few years.
Automotive suppliers are similarly following suit. For example, Japanese automotive supplier Fukai Toyotetsu Indiana Corporation will be investing $56.9M to expand its Indiana operations. "
Here you can see how the US economy has divorced itself from the rest of the world, and has been rapidly rising in contrast, so the trade negotiations have at the very least not hurt the huge quarterly 4.1% GDP growth: https://i.imgur.com/5luvlHc.jpg
On top of that the rise of electric powertrains is a game changer. No, it's a tournament changer.
No, its entirely irrelevant. Electric cars make up... wait for it... 0.15% of vehicles on the road today.
That's right, not even 1%, and they aren't primary cars for that tiny fraction, as the target demographic tends to be wealthy households that keep them around as third or fourth vehicles.
Hybrids and plug-in hybrids are infinitely more practical, and diesels are still hugely popular in the EU with as high as 66% of road going vehicles being diesel powered in France for example. Electric has too many compromises and it is far too wasteful to have extra vehicles around because the electric can't always meet needs due to limited range and inability to achieve rapid recharge for road trips or even just parking in front of the house for the week going to work, since it needs to be consistently plugged in every evening causing a need for car shuffling in the drive way and competition in large family households where mom, dad, and their 2.5 children have cars in the highschool years and still visit after.