Is this a scam?

I very much doubt that it's legit.

What company is supposed to be giving out these iPhones?

What is "a bunch of other winner responses"?

What are they asking you to do about it? That's where they would be harvesting personal information, or asking for money supposedly for the shipping or some administrative fee.

At the very least, answering them in any way tags you as a possible target, and your name goes on a list for sale to some other scammers.

+1.

Generally, if you get mail telling you that you are a "winner" of some contest that you never entered, it is a scam or deceptive ad of one sort of another.

When car dealers do things like this, and you have to bring the mail to the dealership intact, to have them scratch off stuff there to reveal the "prize", the gimmick is that the chances of getting a worthwhile prize are almost ZERO. The chances of being subjected to high-pressure sales pitches, on the other hand, are pretty good.

With online stuff and e-mail, you'll discover that there are all sorts of "fees" to collect your "prize"; assuming that the "prize" is even real at all. Or there will be lots of weasel wording saying that you are the winner of a chance to win a prize (which isn't remotely as valuable as winning the prize itself!).