Two divisions wouldn't make that enormous a difference anywhere on the front, not when Zhukov's in charge of the defense of Leningrad and 1,000,000 died in the city as it was. Two more divisions in front of Moscow just worsen the German defeat in the winter there, two more divisions in the south aren't going to alter German weaknesses there given the bulk of Soviet troops in 1941 were also there.
It represented a panzer corps (plus 500 aircraft) by the africa corps not being created
now in the late september battles of course they would have meant nothing in the grand scale
however, having them attached to 4th panzer army at the start of barbarossa possibly allows Hoeppner to capture Leningrad
Manstein blew through the Baltic Military district advancing 250 miles in 5 days; when he came to the Dvina river he stopped because he had nothing to screen his flanks even though there was very little in front of him
Voroshilov (idiot) sent all the forming militia and anyone who could carry a gun (although many didn't have guns) in a panic move to try and form a defensive line on the river; adults in the stavka (Zhukov) ordered this counter manded and withdrew the infantry closer to and inside the city itself where they wouldn't be vulnerable to encirlcement in open country
Manstein sat on the Dvina river for 5 days waiting for other elements of the army to catch up so he could resume the advance, and this allowed the russians to rectify their mistake and still have forces able to defend the approaches to the city
Had the africa corps forces been on Manstein's right flank, they along with Manstein's 56th panzer corps could have launched a double envelopement against the militia divisions on the northern bank of the river, pinned them against it and compelled their surrender which would have effectively left no fighting forces between themselves and Leningrad, which in turn probably allows them to capture the city off the march a la Orel