According to Google's new AI:

The attack on Pearl Harbor wasn't caused by a single disagreement, but rather a buildup of tensions between the United States and Japan for decades. Here are some key points:

• Competing Interests in Asia: Both countries wanted access to resources and markets in China and Southeast Asia [National WWII Museum]. This led to friction as Japan invaded Manchuria and later most of China.
• U.S. Opposition to Japanese Aggression: The U.S. disapproved of Japan's military expansion and imposed economic sanctions, including an oil embargo, to pressure them to withdraw [Asia for Educators].
• Resource Scarcity for Japan: Japan needed oil and other resources to fuel its war machine. The embargo threatened to cripple their military [Imperial War Museums].
• Failed Negotiations: Diplomatic talks between the U.S. and Japan broke down as neither side was willing to concede [National WWII Museum].

Japan's leaders hoped a surprise attack on Pearl Harbor would cripple the U.S. Pacific Fleet and force them to negotiate a peace that allowed Japan to continue its expansion. Their gamble backfired, uniting the U.S. in anger and leading to America's entry into World War II.

I thought it was copper? Ah, looks like both were factors. And we wanted them to leave all their neighbors alone.