That would be deliberately provocative, something his opponents won't hesitate to use. What he needs is a clear, unambiguous, unprovoked attack on an American base or American territory.
Exactly. It must be kept in mind that in 1941
IOTL the POTUS did not- as he does now-
have unlimited power in the field of foreign
affairs. One reason was that the US millitary
was far, far weaker than it is today(to a
degree that today we can’t even imagine).
Second, & even more importantly, was that
the Congress- again, unlike today- actually
took its responsibilities in foreign affairs ser-
iously. It actually sought to keep Presidents-
for good or bad- under control. Thus unless
like you said Saint you had a clear, suppos-
edly unprovoked attack on America there
would have been no shortage of people in
Congress who would have jumped on FDR
with everything they had & refused to go
along with him.