Mazda is Maz-der to me... Nissan is Ni-san... though after a few hours of watching US motor-racing you get used to Marz-da and Nee-saan. Also I normally pronounce Acura as Hon-der.
The Japanese names are interesting ones because the Japanese vowel sounds are always pronounced the same way.
A is always an "ah" sounds, I always "ee", U always "oo", E always "eh" and O always "oh"
So Mazda would be "Mahz-dah", Nissan "Nee-sahn", Honda "hone-dah" etc.
Which
look like the American pronunciations, but Americans tend to draw out their vowels, whereas the Japanese words are quite curt. So Nissan is exactly as it's written phonetically - not "Neeee-sahn" as it is in the American tongue.
At least, I'm pretty sure that's how it works. Famine is better versed in Japanese than I am, so he'll probably come in and correct me...
Of course, the way you pronounce something day-to-day is however you pronounce it. It took me years to make myself say Porsche correctly.
As for French names, Americans tend to murder them somewhat. Michelin is most amusing, but even the British ads get that one wrong. Correctly said, it should be "meesh-lan", but I've heard "mich-lin", "mich-el-in" and all sorts.