If you expand your view, you can see things better.
US regime is already spread too thin around the world. They can not sustain this situation for long specially since they are hemorrhaging money, in trillions. They need to reduce their costs at some point and that means abandoning some of the wars they are participating in specially when the problems pile on back home.
Also since according to all the National Security thing they release, China is on top of the lists of countries US has to declare war on, they will shift all their focus to East Asia sooner or later.
Well, let's broaden our view. The USSR, and then after its collapse Russia, have always been strategic opponents of the USA, and all the time after World War II the USA was preparing for a military confrontation with Russia. Russia's attack on Ukraine, the heroic and often effective resistance of Ukrainians to Russian aggression gave the USA the opportunity, with the hands of Ukrainians, if not to destroy their main potential enemy, then significantly weaken it to such an extent that Russia will no longer have such a big influence on the international arena as it did before. By helping Ukraine, the USA spends only material resources, while saving the lives of their soldiers, since the USA is not yet involved in a direct military contract with Russia. At the same time, the effectiveness of American weapons on the battlefield in Ukraine and, accordingly, the weak effectiveness of Russian weapons, led to the fact that third countries refuse to purchase weapons from Russia and buy them from NATO countries. And this, in turn, led to a sharp increase in the military-industrial complex, an increase in jobs, and so on.
The only thing that the USA still fears is the loss of control over nuclear weapons in the event of the collapse of the Russian Federation. Therefore, the US is not yet providing Ukraine with weapons in the required quantities and assortment, which can lead to a quick victory for Ukraine on the battlefield. But all these red lines are in motion and changing, which was demonstrated by the successful invasion of the Ukrainian Armed Forces into the Kursk region of the Russian Federation and the Kremlin's realization that this is for a long time, and also showed the world the far-fetched greatness of Russia.
On the other hand, the US cannot allow Russia to win the war against Ukraine. This would simultaneously mean the defeat of the US and its allies in the international arena, and the defeat of the US military doctrine, and a departure from the values it advertises, and the need for further military confrontation with Russia after it licks its mortal wounds and gets stronger. The only question is in what format this defeat will be recorded. And Ukraine has already proven that it is a good combat shield for NATO from Russian aggression.
Also, if the US allows Russia to win, this will significantly strengthen the positions of China, Iran, North Korea and the Russian Federation, their military and economic alliances and launch a new round of deadly wars on the planet.
