The long and the short of it was Ambassador Joseph Grew, the American embassy staff, and their families were interned by the Japanese. They were essentially prisoners within the American embassy, subject to continued surveillance by the Japanese police and had to follow a regimen of petty rules. Food was spartan and the internees struggled to make the best of it through constant card games, reading, and the construction of a single-hole golf course. Grew's diary, published postwar as Ten Years in Japan, described the numbness of routine and Japanese stonewalling of negotiations for their repatriation.

But they were repatriated by July 1942 as part of a larger reciprocal exchange between the Anglo-Americans and the Japanese in which ambassadorial staff trapped in the US, UK, and Commonwealth were exchanged via neutral states. Unlike other civilian internees, there were customs and norms for their treatment and eventual exchange. While Grew and company described their internment as prison-like and their material conditions were worse than the internment of their Japanese counterparts in the US, they were able to leave Japanese territory in little more than six months after hostilities started. Non-diplomatic internees such as civilians trapped in China or the Philippines largely had to wait until the end of the war.

I've previously addressed this here, and even if you don't pull the full oral history that I linked in it (which I'd recommend as it's a great read), the excerpt from it in the ADST interview of Joseph Grew's private secretary was made 50 years after Grew published and thus provides a vastly more unfiltered look at the day-to-day life of Embassy staff while in lockdown.

In short, though, they survived fairly well if with many compromises and an awful lot of boredom until the two staffs were simultaneously repatriated - Grew's cold shouldering of his counterpart when they briefly met each other while transferring ships is notable, along with a sub nearly killing all of them - but the American reporters unlucky enough to be in Japan were tortured until they took part in the exchange.