Act of terrorism?

[Winchester]

IIRC The mailbox is actually considered property of the USPS which is a government entity. Therefore if you tamper with the mailbox you are tampering with the USPS.

Title 18, United States Code, Section 1705


Whoever willfully or maliciously injures, tears down or destroys any letter box or other receptacle intended or used for the receipt or delivery of mail on any mail route, or breaks open the same or willfully or maliciously injures, defaces or destroys any mail deposited therein, shall be fined under this title or imprisoned not more than three years, or both.