Indeed in the financial sector in Japan regulators require immediate disclosure of issues. I've been there and the FSA doesn't tolerate even 24 hours delay. So why would Japanese car maker expect any differently in the USA.
In any case here's what should have happened:
1) immediate disclosure and recalls as soon as issue identified.
2) disclosure to appropriate regulators as soon as possible.
3) autonomy to the US corporate leadership to get the word out quickly. If you don't have the right person in the job or can't trust him (or her) - then get someone else?
But let's also keep things in perspective. Other car companies have also had these problems. Remember exploding gas tanks on the Pinto and accelerator problems on Audi's? There was a joke about not wanting to be between the two!
Also what if GM had a similar problem. Doesn't US ownership of GM present a conflict of interest with US regulators? Would the Dept. of Transportation response be as robust? Just asking!