Can i join the army with asthma?

No, you cannot join. Imagine the scenario. You're in a firefight and suddenly, you have an attack. Now you put your guys at risk because no one knows what's wrong with you and you have no inhaler and are 12,000 miles from the nearest one. You're dead, your unit will get shot up because you tried to hide it. There are other ways to serve, try something like working for the VA.