Finkface

No one is disputing that a Nexus card meets the requirments to enter the US or Canada as far as the WHTI. But airlines are free to make their own rules as to what they require. If you look in the Nexus thread, there are loads of reports about which airlines not to use if you want to travel with a Nexus card alone. Porter springs to mind. And is this really the fight you want to have as your flight is boarding? You may (but more likely will not) win eventually but you probably won't be on the flight you planned to be on.

Even the CBP and CBSA tell you to check with your airline first as they may require you to present a passport.
https://help.cbp.gov/app/answers/det...al-information
Under theWestern Hemisphere Travel Initiative(WHTI), the NEXUS card has been approved as an alternative to the passport for air travel into the United States for U.S. and Canadian citizens. However, if you are traveling without a passport we advise that you contact the airline first.

http://www.cbsa-asfc.gc.ca/travel-vo...v-eng.html#_s1
Acceptable documents to denote identity and/or citizenship
You should carry a valid Canadian passport for all visits abroad, including visits to the United States (U.S.). A passport may be required by your airline or alternative transportation authority, as it is the only universally-accepted identification document, and it proves that you have a right to return to Canada.

No, you really aren't. 'Technically' or otherwise. You are pre-cleared for entry into the US. That's all.