Is an asthma attack similar to a seizure?

No, not in the least.

A seizure is caused by many things, and is abnormal overactivity of neurons in the brain, causing the 'Tonic-Clonic' activity, or 'Grand-Mal Seizure'.

An asthma attack is brought on by irritation to the airway, in which the bronchioles constrict and inflame, and later produce excess mucous. It is a respiratory disorder, whle a seizure is a neural emergency.