The WA state patient entered the US on January 15th
according to news reports; the screening at US airports started on the 17th.

https://www.google.com/amp/s/www.kir...outputType=amp

It it unknown if the screening techniques would have caught the problem at the airport. What is known is that the virus will jump from human to human.

The sick person took some sort of shared transportation from the airport.

I was in Snohomish County WA recently but left the day the infected person arrived.

Although I am not in a flu risk group (65 or older or immune system compromised) many of the my clients are 65 and older and I am more concerned about the risk to their health than I am about the CDC legality of screening; but that is just me.