A) This is already the case for basically every phone for sale, and thus isn't really applicable to this article. Also, I thought the modem was by Qualcomm?
B) Sure, they could ban all Chinese made devices but that would basically mean banning all devices. Pixels are made in China just like Motorola, so again, not much of a difference here (I'll allow that there may be a difference of just how much of the phones are made in China.)
C) How is the government going to ban the use of an open source OS? And why would they? Apple has spit in the government's eye a few times and yet they don't ban iOS.
A and B) Sure, but you said it yourself: that how much is a significant factor. And Pixels use Samsung modems, not Qualcomm
C) How does the government ban anything? Through legislation and enforcement. That can take a number of different forms