Ultimately the only reason they attacked was because they were Japanese supremacists and racists.
Which is at the core of
hakko ichiu, everyone else was seen as a bunch of inferior nitwits, destined to be subjugated and ruled by them.
And no, the US didn't bring on the war.
Which is the correct answer, especially when FDR is blamed for an oil embargo on Japan. That's a leftist blood libel that's been making the rounds for at least the past 80 years. Metro-area newspapers at the time even parroted that in their editorial sections. Surprised and chagrined when it manages an appearance on the threads of FR. There was a provision in Japanese law where under a declared state of emergency the military could assume control of the nation, with the civilian government taking the backseat into an advisory role (if that). Post World War 1 the military stepped up their sabre rattling, looking for an "emergency", any emergency that would do. They got so carried away that plans were made for a full-on coup around the mid 1920s, dashed by the appearance of a very destructive hurricane, making organization impossible. When you study the details of the political dynamics at work in Japan in the early 20th century, you can arrive at a sobering conclusion that if a few things would have gone differently, World War 2 would have kicked off a lot sooner than it did.
The post-WW1 diplomatic policy tiffs with the US, as well with other outside powers, played into the domestic schemes of political exploitation by belligerents in the military and their civilian sycophants to gaslight and manipulate the public into heightened paranoia about the intents of outsiders (i.e. US, Europeans) in their hemisphere, into believing that a stronger role by the military was needed, and NOW, not later, to protect against foreign interlopers. Regardless of all that, we were always in their plans, as well as other 'outsiders', from a perspective of strategy as well the belief that we were inferior adversaries who must be shown who's boss and put in our place.