The Universe has to be the way it is, open before such an intelligent being, Adam, who is bestowed Rooh: Divine Energy from which free will has been given to him. It is true that humans are earth-bound, but, they have put their feet on the moon, and their spacecrafts have crossed the boundaries of our solar system and are traveling in the interstellar regions of space.
27:93 And say, “All praise is due to God! In time He will show you His Signs, so that you will recognize them.” And your Lord is not unaware of whatever you do.
41:53 In time We will show them Our signs in the utmost Horizons and within themselves, so that it will become clear to them that this Qur’an is certainly the truth. Is it not enough for them to know that your Lord is Witness to all things (including this proclamation)?
[9:31-33, 13:31, 14:48, 18:48, 41:53, 48:28, 51:20-21, 61:9]
Humans are gifted with Divine Energy and they deserve a better state of being, they are created for Paradise. In order to achieve their Paradise they have to follow Allah's Guidance. They need to believe in the guidance and do works that are consistent with Allah's Laws. But if they fail to realize this reality and follow Satan, their selfish desires, they only hurt themselves and not Allah and the Believers. That is because they choose to exercise their Free Will for instant gains and low benefits and as a consequence degrade their state of worth and honor.
3:133 Move forward eagerly to the tranquil security that comes from your Lord, and to the Paradise that transcends spatial boundaries, encompassing the heavens and earth. It has already been prepared for those who live upright, [Paradise is not confined to the skies. Like Hell, it begins right here in this world]
3:134 And for those who, in ease and in adversity, keep their resources open for others. They divert and sublimate their anger and potentially virulent emotions to creative energy, becoming a source of tranquility and comfort to others. They pardon people gracefully. God loves the benefactors of humanity.
"How do our actions affect the Universe? Is not our existence less than minuscule in the incredibly vast expanse?"
Our actions affect our view of the universe. Our actions affect our understanding of the universe. Our actions cause balance or imbalance on our "Self" which is a part of the universe. Our actions may cause deafness in our ears and blindness in our eyes, then, how would it be possible for us to hear the sounds in the universe or observe the heavens above ?! The Universe is the Truth, created with a purpose and working according to Allah's Unchangeable Laws. It is we humans that may reach a point when no longer the universe can affect us. The state in which the Universe and the Truth won't be able to cause humans to change their condition, simply because they themselves persistently rejected the Truth and realities in the Universe, and will surely fall for destruction.
Have nice times :-)