https://www.fbi.gov/investigate/counterintelligence/threat-intimidation-guide

There is no single, standard “response time” for a “Tier 1 threat to America.” The timeline depends entirely on the nature of the threat: [1, 2, 3]

• Direct Military Attacks: For immediate, kinetic threats (like an incoming missile or active invasion), the U.S. military is designed to respond instantly. Strategic response systems react in 30 minutes or less(e.g., ICBM tracking), while rapid-reaction forces like the 82nd Airborne can deploy globally within 18 hours. [1]
• Cyber & Infrastructure Threats: For digital or critical infrastructure incidents, federal guidelines require major agencies to immediately detect and log incidents, with responses scaling in severity from hours to days. [1]
• Travel Advisories: For overseas personal safety, the U.S. State Department updates advisories continuously, warning travelers to avoid “Level 4” (Do Not Travel) countries indefinitely. [1]
• Intelligence Reporting: For strategic, geopolitical assessments, the U.S. Intelligence Community issues an Annual Threat Assessment, which establishes the administration’s long-term response priorities rather than an immediate emergency clock. [1, 2]