The Germans sunk the Reuben James in October of 1941, we almost declared war on them then.
FDR knew it was only a matter of time.
Once Britain declared War on Japan, it was a moot point, since all restrictions on aid to Britain were gone.
And that was actually pretty good indicator that we were not going to do so.
And there would have been a major push to cut any aid to the UK except maybe for their troops in the Pacific. And that was only a maybe. We really did not want to get into the war in Europe. Certainly we did not want to get involved until Japan was dealt with.
And the US president sending vital war material to the UK when it was needed for the Pacific would have been a sure way to get himself in hot water.