Why should any US cop worry about being subject to Canadian law while in Canada?
There is a significant problem in the US with the militarization of the police and the overuse of heavily armed police in no-knock raids. I bet this is the kind of thing the US is concerned about. Let’s not import this problem into Canada.
If Canada gives in to US demands on this issue, Canada becomes no more than a vassal state, not unlike how the old Eastern European Countries were brutalized by the USSR.