What an Argentine attack on Britain would change

What would have happened if Argentina had attacked the British mainland during the Falklands War?

Britain would retaliate directly, strengthen home defence, gain stronger American backing, and probably rebuild the fleet on a much larger scale.

The counterfactual assumes Argentina somehow possesses the reach to strike Britain, which immediately broadens the war. Vulcans and carrier aircraft would be used more aggressively against Argentine territory, while the United States would find neutrality much harder to sustain. Britain might add Patriot batteries or comparable home defences if the attack exposed a domestic vulnerability. Politically, the perceived failure of earlier cuts would probably trigger a major carrier and fleet rebuilding programme.