Final answer:
Methamphetamine, commonly known as meth, is the leading problem drug in the United States, associated with severe health risks and a high potential for addiction.
Step-by-step explanation:
The addictive stimulant that has become the leading problem drug in the United States is methamphetamine (meth). Meth is highly addictive and can be made from over-the-counter medications containing pseudoephedrine. Methamphetamine abuse leads to intense euphoria and pleasure, especially when injected or smoked. Meth use is associated with severe health risks such as 'meth mouth', skin abrasions, memory loss, sleep problems, violent behavior, paranoia, and hallucinations. Stimulant drugs like meth impact the brain's dopamine neurotransmitter system which is associated with reward and craving, leading to a high potential for abuse and addiction.