Kutscha, you're being unduly pessimistic.
There was more time to get to Tunis than you give credit.
Only Recce troops and anti-tank guns arrived on 14 February.
The 5th Light Division's tank regiment did not arrive for nearly a month after that - March 8 and 10. They would have had to fight their way ashore against dug-in Matilda IIs and anti-tank guns
The first Canadian built Flower Class corvettes were commissioned in November 1940, and they did actually save the convoys.
see
http://www.hazegray.org/navhist/canada/ww2/flower/
The USA contributed the square root of FA to the early battle of the Atlantic - few of the 50 rust-bucket four-stackers that were sent in exchange for bases were actually used, and only after they had been refitted at great expense.
Dive-bombers would have been needed when the British Army eventually met the Germans, if ever - which is the point you're overlooking.
Tony