Yes, American Yew is toxic to dogs!
Dogs accidentally consuming the American Yew plants can show the following clinical symptoms: Vomiting, Prolonged Depression, Incoordination, Hypersalivaton, Sleepiness Or Excitation, Dilated Pupils, Low Body Temperature, Low Blood Pressure, Coma, Seizure And Death (In Rare Cases).
American Yew consumption is also toxic to Cats and Horses.
Toxic Principles Of American Yew: Taxine A and B, Volatile oil.
More Info About The American Yew Plant
Scientific Name: Taxus canadensus
Family: Taxaceae.
Also known as: Canada Yew, Canadian Yew.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.