Both attacks were carried out on American soil and caused intense public outrage that pushed the U.S. government into major military action and a new phase of war.

Core common points

  • Attacks on U.S. soil
    • Pearl Harbor (December 7, 1941) struck the U.S. naval base in Hawaii, which was (and is) U.S. territory.
* The 9/11 attacks struck New York City, Washington, D.C., and Pennsylvania, all within the United States.
  • National shock and public outrage
    • Pearl Harbor “stunned the nation” and unified public opinion behind entering World War II.
* 9/11 similarly produced nationwide anger, grief, and a strong desire for a decisive response.
  • Trigger for large-scale war policy
    • Pearl Harbor led directly to a formal declaration of war on Japan and U.S. entry into World War II.
* 9/11 led to the declaration of a global “War on Terror” and the U.S. invasion of Afghanistan.
  • Turning points in U.S. history
    • Pearl Harbor marked the end of U.S. isolationism and the start of its role as a leading global military power.
* 9/11 marked the start of a long era of counterterrorism, new security laws, and a reshaped foreign and domestic security policy.

A quiz explanation that asks almost this exact question gives the shared point this way: both attacks were on American soil and caused public outrage.

Quick table: similarities and differences

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Aspect Pearl Harbor 9/11
Where it happened U.S. naval base in Hawaii (American soil). New York City, Washington, D.C., Pennsylvania (American soil).
Main target type Military fleet and facilities. Civilian and symbolic targets (World Trade Center, plus the Pentagon).
Perpetrator Imperial Japan (a nation-state). Al-Qaeda (non-state terrorist network).
Immediate U.S. response Declared war on Japan, entered WWII. Announced “War on Terror,” invaded Afghanistan.
Public reaction Mass unity, support for war after a shocking attack. Mass unity, support for counterterrorism and military action.

In forum style, you could sum it up like this: both Pearl Harbor and 9/11 were shocking attacks on American soil that outraged the public and opened the door to a new, much larger war.

TL;DR: Both attacks hit the U.S. at home, outraged the public, and served as catalysts for major American military campaigns and long-term shifts in U.S. foreign policy.

Information gathered from public forums or data available on the internet and portrayed here.