Not only will Finland and Sweden strengthen NATO, their joining will strengthen their own self-defense capabilities greatly. The old pretend “neutrality” stance of these truly democratic countries was felt to be inadequate given Putin's demonstrated willingness to invade and try to crush sovereign Ukraine. This constituted a huge setback for dictator Putin’s plans. Also these Scandinavian countries joining will hopefully strengthen already significant social-democratic European opposition to U.S. adventurism, and limit our efforts to use NATO inappropriately in other parts of the world.
But of course if the U.S. and major European states lose their will and abandon Ukraine now, while it is still facing bloody Russian attacks, NATO will gradually disintegrate as an effective military defense force — which is exactly what Putin is counting on.
That will have truly awful consequences for Europe and for our own security and standing in the world. It will encourage more challenges from Putin’s Russia, which is now trying to rebuild a new “war economy.” At the same time China, North Korea, Iran, etc. are all watching. They will all feel emboldened if we abandon Ukraine. We will have demonstrated ourselves to be too self-absorbed and too divided at home to be a trustworthy ally abroad.