The US has sent large quantities of food and fuel. Specifically during famine periods (when uprisings would otherwise have been likely) but also at other times. The US gave these goods specifically to the regime allowing them to control the food supply AND keep their forces mobile when otherwise they would have faced a starving population with very limited military capacity.

It's been a very weird thing to watch for 20 years: when it looks like the North Korean system might fail, the US leads assistance to it. Then when it recovers and returns to it's weapons program the US does nothing. That's how we got into a place where North Korea has functional nuclear weapons and will soon have the missiles to deliver them to the whole USA. At that point the US will just have to keep subsidising the regime. It's been decades of mismanagement of the situation over at least 4 administrations.