Not an ingredient -- a precursor. Methamphetamine, pseudoephedrine and and phenylephrine are very closely related:

https://cen.acs.org/content/dam/cen/83/13/8313govpol1imgs.gi...

To convert pseudoephedrine to meth you have to remove a hydroxyl (-OH) group in a way that leaves the resulting molecule in a specific isomer. Doing this at high yield is challenging, but it turns out that if you're willing to live with lots of horrible impurities, you can do it in a cola bottle. PE has the same structure as pseudoephedrine, but in a different isomer, so it cannot be converted with the simple approaches.

Unfortunately, PE is also useless for decongestion, because -- surprise! -- the isomer matters a lot for effectiveness.

As per https://nida.nih.gov/publications/drugfacts/over-counter-med..., "Over-the-counter (OTC) medicines are those that can be sold directly to people without a prescription.". Sudafed—the real Sudafed—is still OTC, by that definition.

The Sudafed behind the counter actually works (really really well), but due to what you've described, you need to present ID and affirm that you'll abide by certain federal laws. Oh, and there's a low hard limit on how much you can buy at a time, which is fine if it's just you in your household but not so fine if absurd levels of congestion run in the family and you all live together.

Edit: I did not say that Sudafed did not also make products containing pseudoephedrine. They do, obviously, it's where their name comes from. They just also make products with useless phenylephrine.