In Canada I'm told liquid formulas (such as bug sprays) can't be patented. I was told it could only be Trade Secreted. How does that work in the US? Are you able to patent liquid formulas?
I suspect what you've been told is not quite correct.
If you have a set of components which, when combined, form a mixture that is novel and non-obvious, then you can certainly patent that (whether it's a liquid or not).
This is true for Canada, the US, and every other country.
However, it may well be that a new liquid formula could be unpatentable due to being obvious. This will likely be the case if the ingredients are used in a known way to achieve a known result with no surprising synergy between them. This of course very much turns on the specific facts of the invention.