Have to say that the Corolla I referred to above is spotless wrt rust. Undercarriage too.

This is all the more impressive given that our roads are salted constantly in the winter months here.

The worst I've seen for it are mid-2000s Fords. It's like the frames aren't galvanized at all, but that may be a problem limited to UK models.

That said my (beloved) Nissan Leaf is starting to go orange underneath but thankfully it looks like surface rust rather than rot.

Subaru is rusted badly. Toyotas didn't have any. Caravan problems are terrible and mostly electrical...window motors have all failed, door locks are failed, weird problems with the car not starting even though battery has charge (starter is fine but the computer refuses to allow the starter to try to work if voltage reading isn't correct). Weather stripping that covers the seams on the roof is all coming off. Anything that is not the engine is falling apart.

  Older Toyotas rust horribly, especially the trucks

My 25 year old Toyota SR5 pickup has no rust at all.