Looks like Kate and family came to Canada.
Ooooh! They are living next door to William and Nellie Anderson in the 1916 Canada census. They arrived in Canada in 1916. Correction added: Kate and family are actually in the same household as William and Nellie.
William Anderson 33 b Ireland
Nellie 33 b Ireland
Tomas 5 b Ireland
Robert 3 b Ireland
Rebecca 7 months b Manitoba
George Buchanan 35 b Ireland
Katie 38 b Ireland
Isabella 1 b USA
1921 Canada census...
St Boniface Manitoba 255 (?) Oak Ave
George H Buchanan 40 b Ireland
Catherine 42 b Ireland
Esabella 6 b USA
Mary 3 b Manitoba
Catheline 2 b Manitoba
The family appears to have gone back to the USA. In the 1940 census they are back in California, if I remember correctly. This census has Isabella b California and a 4th daughter Nellie 17 b Canada. This census should be available through familysearch.org, I think. They are living in San Francisco.
Here it is...
https://familysearch.org/ark:/61903/3:1:3QS7-89MT-DCG3?mode=g&i=5&cc=2000219As an aside, you might check if your local public library subscribes to Ancestry Library Addition. This would give you access to the records but I don't think to the trees.
PB