The UK government argument has been "we're not putting this stuff where a Chinese wiretap would get them anything", as I understand it, it's isolated to low security contexts. And they want Huawei because it's technically superior (needs fewer masts).

The panicky US response makes most sense if the reply they can't say out loud is "but you're putting it in places where it interferes with our wiretapping!"

This is probably not accidental.