This depends largely on what you mean by "enter the war". In August of 1941, Roosevelt signs the Atlantic charter with Churchill that, among other things, calls for "the final destruction of nazi tyranny." In September he had ordered the US Navy to shoot german U-boats on sight. At roughly the same time he begins to articulate a concept of "hemispheric defense" where the boundary of the western hemisphere is just west of the Azores. In March, the lend lease act was signed, which opened the door for the US to fund the enemies of nazi germany. It had been proposed about a year earlier, about the same time the US passed the two ocean navy act, which would have made the US navy bigger than most of the rest of the world's combined.

None of those moves is a declaration of war. All of them together aren't even a declaration of war. But most could be legitimately described as hostile acts by the axis powers, and all were very clearly done with the intent of either getting the US more involved in the war or building up US military power in case of war. Of course, the "US" is not a unitary actor, but was full of lots of different people with lots of different opinions about the wisdom of involvement in the war. It's wrong to say that the US was planning to enter the war, but it's also wrong to say that the US had no plans to enter the war. US leadership, and everyone else, was playing things by ear. The most you can say is that Roosevelt was actively attempting to aid the allies as much as he thought he could get away with politically.