Trump has mentioned Canada as the 51st State many times:

Dec 2024: Mar-a-Lago

Dec 18: Truth Social

Jan 7: Press conf

Jan 23: Davos

Jan 24: NC press conf

Feb 2: Statement

Feb 9: Fox TV

Mar 28: Carney call

Apr 28: Truth Social

May 2: Meet the Press

May 6: Press conf