If Israel unilaterally attacks Iran and Iran responds by declaring war on Israel do USA-Israel accords obligate the USA to declare war on Iran?
The United States is not obligated by any standing treaty between the United States and Israel to intercede in Israel's defense. To date, of the numerous wars that Israel has fought, the United States has only ever provided economic support or gifting weapons. No American Soldier has given his life in an Israeli War. If Iran declared war on Israel, the United States would probably act similarly and may itself declare war on Iran, but this will not be out of any written treaty, but purely based on American regional interests.
The US must do whatever Israel tells it to do.