OK, just remember that gerunds (taking) and objects (us) must follow prepositions.
A simple sentence would be, "WE DON'T TAKE these problems seriously."
Add the preposition, and we need to change a few things (mainly because the main verb and the subject are now a different part of the full sentence - it's no longer "we don't take").
"...the deadly consequences of US NOT TAKING these problems seriously."
It's a very neat way of putting your ideas in a clear order. :)