Can subconscious anxiety be treated?

Yes, sort of: If the anxiety is subconscious it would help to make it conscious in order to address it. This can sometimes be accomplished with relaxation exercises and therapy. But also, since subconscious anxiety affects behavior, adjusting one's behavior can also affect the anxiety. Behaving in a relaxed and confident manner with no unnecessary avoidance can reduce anxiety. "fake it 'til you make it, " helps.