In the US (and Europe, too, I believe) food manufacturers are increasingly mandated to be able to trace their ingredients back to the original source. Each handler along the way is expected to do this, so theoretically there's a paper trail from the beginning to the end on a store shelf.

If there are particular foods for which you'd like this information, I would check company websites and then reach out to producers if that isn't getting the information you want. I can't say how forthcoming companies are with this documentation. Keep in mind trade secrets could be involved that might be violated just by providing that level of specificity.

Inquire with the manufacturer listed on the packaging? There's always some sort of chain to information on packaging, though unless there are laws in place against this, I think we're moving closer to that starting with a qr code than a company name and phone number/address...

Calling/writing to customer service is usually a good start. A lot of this information they are required to have even if they don't need to write it on the label.