If Italy continually retreats to Rome and the US lands troops in Rome on turn 5, even a concerted attack by Austria on Italy most likely cannot get Rome. In both the games I’ve played I did just that- send the bulk of my Army at Italy to no avail. It just takes too long to get to Rome. The best I’ve done is contest Rome- Italy can still build a couple Infantry and the US is landing 4+ units there per turn.
However if instead of going for Rome, you send your initial Venice/Tyrolia/Trieste/Vienna armies straight across northern Italy to get some pressure on Burgundy/Marseilles by turn 3, France will have to split up its forces a bit. This could help Germany enough to have a chance at Paris on turn 4 or 5.
Of course, after the initial armies are sent to France Austria would have to concentrate on making sure Italy doesn’t grow too big.
Germany essentially has to split up its starting forces to fight Russia and France- Austria sends most of its Galicia and Budapest armies against Russia (with small force fighting in Serbia). Ottoman sends Constantinople and Bulgaria armies to Russia.
It could work-