I'd heard about this, and wondered how America squares it with its ridiculously large and expensive War on Terror.

Most of the large petrochemical tanks on the Gulf Coast have bullet dings in them. Folks just like to take potshots at stuff. Luckily the steel of these tanks are already more than thick enough to handle most small-arms fire. They just take the damage into account when they do corrosion monitoring every few years (those impact spots tend to be thinner afterwards, of course).