They are equally legal in the US (Schedule II). Label will usually say something like "Methamphetamine, generic for Desoxyn." It is, however, much harder to find a doctor that will give you a prescription as compared to other stimulants, and some pharmacies will refuse to fill it.
Believe it or not, marijuana (since 2018 only strains containing significant levels of delta-9 THC) is illegal in the US in almost all circumstances, but methamphetamine is legal with a prescription.