We never put a military base in Ukraine, and Canada is a country that is literally tied to the US Defense plan woth NORAD.
Allowing Chinese troops in Canada is basically saying they want to cut ties.
Which benefits the US more then it does Canada.
Because they are now stuck between the US and Denmark with what would now be thoer closest ally, a sea away amd would leave them out to dry.
And you can't really compare Ukraine to canada... because Ukraine has a lot stronger roots to being there and it's land then China does woth anything outside of China