Tatsch was sidelined in the lead up to the Pinstripe Bowl and has yet to return.
Smith was the last man cut from Canada's World Juniors roster last year.
"He has already come in and had a profound impact on the young men in our program."
McCool joins Adie Schneider as the program's first two class of 2028 commits.
Schneider is the program's first commitment in the 2028 recruitment class.
Two of Penn State's most awarded student-athletes continue to add to their trophy cases.