Imagine that every chip China has sold to the US has a hack built in that will allow China to shut them all down. Think of how disruptive that would be. Big things and little things. In a complex system you don't have to bring the whole thing down to have it stop working. If pumps stop working we are talking about water, fuel, even boats. Cars and trucks might stop working. Transportation grids would be in chaos with cars and trucks stopped everywhere. Power plants would shut down. Without electricity water goes down as well. Food goes bad. Video surveillance goes down. Emergency generators begin to run out of fuel after 24 hours. Cop cars, fire trucks, all stop working. Imagine if some of the chips are in the telecommunication network. A lot of phones stop working, routers stop working, internet stops working for many. In a network I don't need to bring the whole thing down for it to crash. If a phone or a computer or a router or a server or a hard drive isn't working it can create a big problem to the part of the network that is working. Could you figure out this was the Chinese, yes, but how long would it take? You would be in chaos and confusion for days which would lead to rioting and looting. Without water and AC people would become delirious within 24 hours. Within the first week you would have cholera, dysentary, diarrhoea, hepatitis A, etc. If you live out on a remote farm you could make do, but if you live in the projects in a big city it will get very bad very quick.