Is asthma a disability?

No.... Asthma is a disease characterized by recurrent episodes of bronchospasm and airway inflammation. However, between episodes, most patients are completely asymptomatic. It is a very treatable disease and does not result in disability even though it is not curable.
Only in severe cases. Asthma is extremely common, meaning lots of americans have it. There is no perfect person, so everybody now or later has some sort of health issue. So, we cannot label a disease as a disability, because that would mean every one of us is disabled. For almost all disorders, there is a wide range of severity . . . And only the severe cases are labeled as disabilities.