Yes, there are huge national security concerns when everybody's cars are always on the network and all fly-by-wire. It would be trivial for anyone who writes the software for these things to include logic or network bombs in them that would enable a catastrophic strike on a country or the rest of the world. Cars being on the network all the time is really a terrifically stupid idea.

Careful readers may note the complete lack of the word "China" in the previous paragraph. But, yes, technically it is even that much more dangerous to have a whole bunch of potentially-hackable robots roaming up and down all your transportation corridors that were also created by your major economic and military rival.

But I don't even like it when it isn't created by your rival, though, because there's no guarantee that your rival can't hack anybody's software. I fear the day when some significant fraction of cars on the road are given instructions to floor the pedal and then do a hard turn to the left 10 seconds later. (Or the right for countries where that is the "turn into oncoming traffic" direction.)

Ask Europe if they think there are "actual national security concerns" about them being so heavily reliant on USA tech companies and services.

I think there are legitimate safety and national security concerns. I also think restrictions are imposed for protectionism / political / monetary reasons. We are living in a world where the people making the decisions wait until there is enough personal gain to act in one direction or another.

There are ways it could be handled. Waymo imports Chinese made Zeekr vans, but Waymo probably replaces all onboard software and hardware.

Just like with the data center 'debate', it's best to assume both sides are just churning out propaganda.