There were around 300 Native American (NA) languages north of Mexico at the time of European contact in 1492 (so we aren't counting those of Mexico or South American such as Nahautl of the Aztec or Quechua of the Inca) of which there are perhaps 100 or so left (and some may only have ONE elderly speaker alive). These languages were often as different from each other as English and Arabic or English and Japanese. Much more different from each other than Greek and Irish for example. So one cannot really say there was no NA word for "god" because there was no one NA language. Of course it also has to do with what you mean when you say the word "god."
The word "god" has a lot of baggage. It originated in the Germanic language family (including English) supposedly as meaning "to call or invoke." The words god/gott/etc was chosen as a Gothic translation for the Greek "Theos" in Wulfila's Gothic translation of the New Testament. Lots of translations and baggage with that word "god."
Here's a couple of examples. In my tribal language, we have two words we use, wakanda and Ma'un. Wakanda is something mysterious, a god, a deity, a power. Literally, it means wa- "something", "kan" that which is so old and mysterious it is beyond knowing, and -da "to be located in a place." Thus the Great Mystery. Our language is Siouan and similar to Lakota and their word Wakan Tanka has much the same meaning. Our word for the Creator is Ma'un, which comes from ma "the land, the soil, the earth" + 'un "to do or make": the Earthmaker. So do those words Wakanda and Ma'un mean "god" the way everyone means "god"? Perhaps. At least many modern people in my tribe say "Wakanda" when they refer to "God."
But in our older tales, Wakanda also meant the Thunder. It was applied to Wakanda in the water/ rivers. A man could even become a Wakanda in some instances. There was a friendly Woman called Nunwakanda, "the Fairy of the Woods."
But we didn't "worship" any of them the way Christians/ Muslims/ Jews worship God as a King or something. We made offerings and kept good relationships, and made sacrifices to drive away illnesses or made vows to achieve special favors. We would "thank", we would ask for favors, such as success in hunting, and always be humble and appreciative. But we never praised or glorified or sang "Hosanna."
At best, Wakanda such as the Creator or Grandmother Earth were favorable to us, their children, and we loved them, honored them, thanked them. The model was of children to father, mother, grandparents.
Some Wakanda were random, unknown, such as Wakanda in springs or cliffs, and those we treated respectfully as you would a stranger who you did not know was good or bad yet. You got to know them by what happened to other people who met up with them. If they were nice, you made an offering of tobacco or some such, and tried to gain favor and help. If they were not nice, you avoided where they were located and took the long way home.