The problem with the terms "God" and "Universe" is as follows:
"God":
To people of faith or belief, they understand what you mean by God and believe he/she/it exists. However, depending on their religious or spiritual beliefs they assign different qualities to him/her/it. In most religious models there is a seperation of God from a human being. Someone saying "I am God" is seen as blasphemy in some religions which assume that Here YOU are and THERE God is. There is a seperation of the two.
To non-believers, non-religious, or non-spiritual people who don't believe in a God or some form of organizing power, the term "God" turns them off because it implies a non-scientific view on life. Science hasn't proven God exists, therefore people who believe in God are about as naive as people who believe in Santa Claus, the Tooth Fairy, the Easter Bunny etc. Therefore, when people of this nature read a book or article which mentions the word "God" in it they usually think "Oh crap, here we go again...he's talking about God... next he's going to start bringing up Jesus and scripture, what a bunch of crap."
"Universe": To believers, people of faith, the term "universe" becomes interchangeable with God in some respect if they understand the context within which it is used. The benefit of using "the universe" is that it implies a oneness between the universe and human bings. Meaning, my body is within the universe, so when I say "the universe" it also includes me and my body and my clothes and the salt shaker on the table and my dog and my cat etc. This is beneficial in understanding the oneness of everything. However, some people who were brought up with the concept of "God" from a religious point of view still think that God and Universe might be seperate. Meaning, if they have a seperation point of view they just say "Well, there is God and then there is the Universe. God is seperate from the universe and everything in it because he created the universe and everything in it." Therefore in such a way of looking at things, it still doesn't accurately describe what is meant. ie. Does that pebble on the road represent God? Can you pick it up and look at it and say "This is God."? If so, you believe everything is God. If not you believe God is "out there" and the rest of the universe is "in here".
To the non-believers, they believe there is a universe and there is no God. Some believe there is matter and then there is energy, while others believe that there is only energy in different forms. In either case, they don't believe that there is a "God out there" that created the universe, nor is there a "God in here" within everything in the universe. They don't see God as being within a photon of light for example, they simply think it's a photon of light, etc. They believe that there are universal forces that keep the universe together, but don't actually believe that there is a unified intelligence that orchestrates everything.
The whole mess becomes very complicated with most people switching between belief, faith, non-belief, and back and forth depending on their mood that day or the situation. For example, a person diagnosed with cancer might not pray to God for healing, instead asking the doctor to book them for chimotherapy, but the very same people, 8 hours later will be sitting on an airplane praying to God when the airplane hits turbulence and the oxygen masks pop out.
A lot of non-believers will also make statements like "Thank GOD you din't _____" etc. but I'm not sure what really means to them.
Some spiritual books I've read actually go through and define "God" or "Universe" with a definition before continuing on with the rest of the book just to make sure people know what they mean.
