Did we expect a war with Japan? Yes, various war warnings were going out to British and American bases in the Pacific and the naval war college exercises for many years before had been planning for a war against Japan. Did we expect an attack on Pearl Harbor? No, I don't think so. Ambushing the Japanese fleet and attacking aircraft would have just as effectively gotten us into the war without losing nearly as many men, ships or aircraft. Also, everyone except for a few crackpots like Billy Mitchell "knew" that battleships were what won wars. They would have been out to sea and the carriers would have been in port if we expected an attack.
A successful attack on Pearl Harbor would have knocked us out of the war before we even got started. The Japanese had targeted the oil depots, carriers, navy repair yard and submarine pens as crucial targets. They'd even designed and built bombs specifically for the oil depots. Turn Pearl into a smoking ruin that the US can not use and we're screwed. As it happened, the Japanese didn't take out the targets they were most interested in.
In the initial planning the Japanese toyed with the idea of a landing party to take and hold Pearl. The idea was dismissed but in the US consideration of a Japanese attack the possibility of of such a landing would have to be thought out.
I've no doubt FDR wanted use to get involved in the war but not at the cost of Pearl Harbor.