Within 24 hours the massive story of the German invasion of the Soviet Union reaches the papers in the United States and immediately brings in the Far Left in the United States in favor of war with Germany.
It wasn't "the Far Left" that was opposed to US support for the Allies against Nazi Germany and changed its tune on 23 June. It was the Communist Party of the USA, and only the CPUSA. The Communists were following the "Party line" decreed by Moscow. Other leftists (notably the "Third Camp" Trotskyites) ignored Moscow's orders. The Socialist Party of Norman Thomas was dominated by strict pacifists and opposed intervention right up to Pearl Harbor.
In Congress, strong opponents to Lend Lease such as Hamilton Fish (R-New York) and Dewey Short (R-Missouri) in the House come out in favor of war as the United States was attacked without warning, while in the Senate, the conservative Republican Robert Taft changes his position as well. This leads to a vote in the House where 100% of the Democrats and 50% of the Republicans vote for war (325-100) and in the Senate, more rally behind the President so it passes with only 8 Republicans voting against.
IMO, it would not be that easy. There would be bitter criticism of Roosevelt for sending US warships into a war zone and exposing them to this risk. Some isolationists would cite Hitler's claim of self-defense by the U-boat, and ask whether
Texas and its escorts "fired the first shot". Others might point out that US ships
had been warned repeatedly against venturing into the eastern Atlantic.
Note that OTL, the torpedoing of USS
Kearny and sinking of USS
Reuben James did not trigger a declaration of war.
There were also some Democrat isolationists, such as Sen. Burton K. Wheeler of Montana, a fanatical opponent of Lend-Lease. If 100 Republican Representatives vote against war, Wheeler would too (IMO).
Again IMO, the votes would be much closer. In any case, while Roosevelt may get a declaration of war, it will be much more controversial than OTL, and (IMO)
highly controversial.
The timing will be questioned. Some conspiracy-minded types may suggest that the
Texas incident was engineered because BARBAROSSA was imminent, and the USSR would need US support.