RE:Canada/US/China césium issues Hey there! There does seem to be a bit of conginitize dissonance going on doesn't it!
To understand whats going on, we need to look at American foreign policy in recent history, which is only now beginning to change. Until now, the doctrine in regards to strategic rare metals was 'keeping them in the ground' whenever possible. If there aren't any mines to exploit, then foreign powers can't exploit them. This worked because at the time China was still playing catchup in a lot of areas technologically and geopolitically, and was just coming into its own as a true global power, and to a certain extent it still is but it is making tremendous strides towards this.
This mentality led to the current situation, where China simply went abroad to obtain its materials and the West is now under-prepared in terms of exisiting resource extraction, as well as the ability to scale it up.
The major shift in policy from leaving it in the ground to strategic production can be seen in the changing American rhetoric towards rare metals extraction and production- a good example was the White Houses "FACT SHEET: Securing a Made in America Supply Chain for Critical Minerals"
I hope this helps!