Question Regarding Ancestry

Bit of a specific question,

I've been a Canadian citizen my entire life, but have off and on been thinking about emigrating to the USA to be closer to my friends, I don't have any real ties here anymore; I understand that Citizenship By Ancestry is for those whose parents are American citizens, but is it able to go any further back? My Great Great Grandparents first immigrated to the USA before going to Canada later on, with my Great Grandmother being born in the USA.

Is any form of ancestry in the USA something that can make the process more straightforward or does it only apply if your parents are citizens?