There were plenty of things Hitler could have done differently. Once he was in Russia, if the Russians were counterattacking, though, there would be limits to how many troops he could siphon off to fight in Africa.
Sure, he could have skipped declaring war on us and let us take that step, promoted rebellion in the Middle East and India, and gone for Moscow (or the Caucasus?), instead of Stalingrad, and that could have helped him. I'm glad he lost in the end, though.
Even if Hitler not declared war on the US, it really wouldn’t have mattered.
Britain declared war on Japan right after we did, thus any restrictions on arming Britain were gone....only a matter of time before the Germans sank one of our ships giving us the Casus Belli to declare war on Germany.