In theory? Yes.
The USSR was hampered by poor leadership early in the war, with most of its military wiped out in the initial Nazi attacks, with something like a 30-1 advantage on the German side in destroyed planes alone. There were a variety of reasons for this, but the purges, Stalin's general refusal to believe the reports that an attack was imminent, and general incompetence really hampered the Soviet military at this stage. Piling right on top of all of that was that the Soviets had moved into Poland previously, abandoning their older defenses for positions inside Poland which had not been properly fortified. Much like the Fall of France the circumstance really meant the USSR was fighting on the back foot for years. Fix these issues and the Soviets could have stopped the Nazis in 1941. Hell, have a few decisions from the Nazis change (for example, don't divert soldiers south to Kiev and the Nazis are left with a massive flank that can't be defended), and this could have happened anyway. Lend-lease made up for a LOT of the losses from this stage of the war, but with better luck and more competent leaders many of the losses probably could have been prevented in the first place. When does the war end? Probably 1943 or 1944, depending on Soviet losses early on. With more of the Soviet forces intact, and more German losses, as well as the Soviet industrial heartland and agricultural area untouched the Soviet advantages can really be brought to bear. Now, the interesting thing here is that in theory Germany and the Soviet Union are evenly matched, but German inefficiencies mean the Soviets are going to outproduce them drastically, and have a higher population to call to arms. Stopping the Nazis early also means far, far less slave labor for Germany to use in upping their production later in the war, meaning the differences will be drastic even without lend-lease.
The US has a tougher time for two reasons. First, and most obvious the sheer distance between North America and Nazi Germany. The perils and difficulty of a trans-oceanic invasion are fairly well-known, but it requires a truly colossal understaking, especially if the enemy is fortified and numerous enough. Compounding this is the second factor, the miniscule American army at the beginning of WWII. There were something 100,000 active duty soldiers when WWII began, making the American army about the same size as Romania's, and this mean a HUGE expansion was needed, which came with its own growing pains as officers had to be promoted to new positions, and millions of people had to be trained. All of this adds time for the Nazis to fortify. Had the US had an army on the size of say...Italy's (3,000,000) then the American Army might have been able to quickly sweep in and secure the coasts of France before shipping in the main body of the army early, before the Atlantic Wall had even really begun. As it was though it required years for the US to even really get started, which is where the difficulty comes in. So ultimately any solo war between Nazi Germany and the United States is basically going to lack ground combat most likely and instead be a war of economics, naval clashes, and air battles. All of which the Reich is doomed to lose due to the VASTLY larger American air and naval power, as well as the American economy dwarfing that of Germany (and everyone else, but that's beside the point). How does the war end? Most likely with German economic collapse. The Nazi economy was stupidly innefficient. As mentioned above they were outproduced by Britain in virtually every category for YEARS due to these issues, despite having larger economic power in theory. When put up against the industrial giant that was the United States there's no way they can win. How long does this take? Honestly, no idea, but quite a while, meaning victory is far slower than in the Soviet example above. Or the US develops a few dozen/hundred atomic bombs and burns the continent to the ground.
Right, I mentioned this. Britain alone outproduced the Nazis for at least a couple of years, only really lagging behind in small arms (which aren't nearly as important as the others.) It wasn't until 1944 ironically enough that the Nazi manufacturing picked up significantly enough to overtake Britain. And it never even came close to that of the USSR or US.