A better scenario would be for the sub to start in France, transit across the Atlantic and intercept the CVBG without detection or being followed by one of our own.
In wartime you don't send a CVBG in an area of probability that has a known untracked sub in it.
Plus one torpedo is not going to SINK a CVN. It could damage it and send to to dry dock but it is not gong to sink it. You do not conduct CVBG ops or amphibious operation until the ASW situition under control. Just like the Air Force doesn't send in level bombers or attack aircraft into a battle until air superiority has been established.
Bubble heads know in wartime that the sub would have been trailed all the way across the Atlantic and sunk WAY before it got anywhere near Florida but they won't tell you that.
I said missiles not torpedoes.