Alexa and Chris haven't lost to another US Pair internationally this entire quad. The only time a US pair has ever beaten them is 2016 US Nationals. After that competition, they went to Four Continents and scored the highest LP score (and eventually the highest SP score in Boston) that any US pair has ever received under the new judging system. They're all inconsistent and some of the newer teams are completely unproven and nothing but hype so far.
If we send anybody else but Alexa and Chris to the Olympics, I think the international (non-US) skating community would be completely scratching their heads.

It's not that our other teams aren't very good, but we only have one spot and nobody else can score as high as the Knierims on an off day. An off day for any of our other pairs means not advancing to the long program, right? All just my opinion, but it's an extremely strong argument to send Alexa and Chris no matter what happens at Nationals IMO.

I don't see any of our teams challenging them internationally this year unless something drastic happens. I get that people might just like another team more, but, well, get over it quite frankly.
It is what it is and we only have one spot for Pyeongchang with a bronze medal in the team competition on the line. A 10th place in the SP from Cain and Leduc really won't cut it.