Like our own anti-missile defenses, missiles are expensive and take time to replace.
Drones, however, are cheap and Iran was cranking them out for Russia and other allies. I doubt they'll be running out of drones anytime soon.
Additionally, the greater danger is that the Iranians have loaded dozens of drones aboard cargo container ships with the option of launching them from 500-1000 miles offshore. Large coastal cities would be the most likely targets: LA, SF, DC, NY, MIA, etc.
The purpose of terrorism is to terrify. Just putting one drone into the center of a city in enough to start a panic for a nation that has relatively few military or veterans, most of whom are over 65 with about half of those disabled.
en.wikipedia.org
The veteran population in the U.S. is changing and facing new challenges that cannot be addressed with outdated approaches.
riponsociety.org
Today, there are about 17.5 million veterans in the United States, representing roughly 6–7 percent of the adult population. That’s a dramatic shift from the decades following World War II, when veterans made up 10–15 percent of U.S. adults. By 2040, that share is projected to drop below 5 percent, and the total veteran population is expected to fall to around 13 million....
...The population is also aging. Nearly half of all veterans are over the age of 65, and more than 40 percent live with a service-connected disability. Many are managing the long-term physical and mental health consequences of service, from chronic pain and toxic exposure to post-traumatic stress and traumatic brain injury.