Why is Israel being constantly attacked on its soil? First of all because it's been aggressively expanding its borders to the expense of the local Palestinian population for the past 65 years.
Secondly Israel is a theocratic state, where citizens of different religions have different sets of rights, where the situation has been described by Israeli commentator as bordering apartheid.
It's extremely misleading to say "If Arizonans were to start firing dozens of rockets a day at California…". The Palestinians have not started randomly bombing Israel out of the blue.
Also I wouldn't use the Israeli in Gaza as a paragon of virtue: I don't think that California would start using phosphorus bombs against Arizonan civilians, since it's explicitly forbidden by the Geneva convention. But since the US have actually used phosphorus against civilians in Fallujah in 2004, maybe you're right, they would be less civil.