Unfortunately, having a long history of Canadian descent isn't a factor in determining whether or not you are a Canadian citizen. Assuming your grandparents were married, your family's citizenship history would be as follows. Your mother's parents were born in Canada as British subjects, but your grandfather ceased to have that status when he became a U.S. citizen in the 1930s. In 1945, your mother was born in the USA to a U.S. citizen father. She was not a British subject, because her father was not. In 1947, when the Canadian Citizenship Act took effect, only your grandmother would have become a Canadian citizen, because she had not yet become a U.S. citizen. (Your mother would not have inherited Canadian citizenship unless born out of wedlock to a Canadian mother. Otherwise, the child's status was determined by the father's.) In 1954, your grandmother ceased to be a Canadian citizen. As of the changes in 2009, your grandmother would have gotten her citizenship back, and as of the the 2015 changes, so would your grandfather. Your mother also became a citizen again in 2009, but the 2009 changes instituted a rule that limited citizenship to the first generation born abroad. Because you were born in the USA in 1973 to a parent who was also born in the USA, and who was not a Canadian citizen when you were born, you were not a Canadian citizen in 2009, which means you are not a Canadian citizen now.
