"It seems that you are arguing a different point, which is that the NSA could well tap undersea fibre for the purpose of spying on other governments."
Yup. I'm not arguing for or against the NSA tapping the specific NSA cable in question. I have no idea if they've done that. And I don't know why they wouldn't just tap the US end of the damned thing and be done with it.
I am arguing that the idea of tapping an undersea cable - if it was determined that there was a practicable need - is not outrageous. That's all.