There are three mistakes you’re making in those two statements, and an indication that you made a fourth.
What makes you think false advertising or doctoring food with cheap filler is an exclusively American thing? I gave two before, here’s another that is both more recent and not in America: Chinese Milk Scandal.
Why would you assume the people buying bread with sawdust knew it had sawdust in it? Do you suppose it was listed in the ingredients, or do you imagine the people who are buying the cheapest bread they can find have the time, means, or knowledge to determine their food is in fact doctored?
You pose questions like it’s unlikely that something would ever happen when being provided with knowledge that that thing did in fact happen. At this point I can only assume you’re trolling or willfully ignorant.