"Personnel is policy", and blaming and finger-pointing is an excellent way to make personnel changes when you are not the appointive authority.
Phlegmatic appointers and other managers, and ignorant voters who elected the wrong guy, need to be motivated by "heat" to make necessary changes.
So she's going to fire Mexico and replace them with -- who?
If the idea is that it's the leaky border that makes for drug problems and we need to replace the politicians who made or left the border porous -- fine.
But the who do we blame -- Mexico or the US? -- angle isn't worth much.