The NAEC is an event bringing together the Cascadia Dirt Cup, the Idaho Enduro Series, the Montana Enduro Series, the BC Enduro Series, and MTB Enduro (Mexico). The race will be held at Silver Mountain, ID on June 11-12. More information is provided in the links below. Registration opens on February 17, and this race will sell out well in advance.

From the press release: North American Enduro Cup 2016 - Pinkbike

A whole new international enduro race is coming to North America on June 11 and 12, 2016: The North American Enduro Cup!

Registration opens on February 17, 2016! More details can be found at our website:
North American Enduro Cup

The Cup is a completely unique event. It features five of North America's premier enduro race series coming together for a 2-day competition at Silver Mountain in Kellogg, Idaho. The Cascadia Dirt Cup, the Montana Enduro Series, the Idaho Enduro Series, MTB Enduro, and the BC Enduro Series are all taking part and have been working together for months to create this championship event!

The North American Enduro Cup championship titles will be awarded to individuals and teams. The Cup will also serve as a bonus race for participating series and racers can score individual points for their home series.

The Team Competition:

Team results will be calculated using the times of every team member on every stage. The cumulative time of all team members is combined for the overall ranking; the lowest combined cumulative time will be crowned the North American Enduro Cup Champions.

Professional category teams must be comprised of racers from the pro ranks and be of the same state, gender or co-ed. Amateur category teams must be comprised of racers from the amateur ranks and be of the same state, gender and co-ed. Teams may consist of racers from different sub-categories. Subcategories consist of Hardtail Open, Jr. Boys, Jr Girls, Jr. Expert Boys, Jr. Expert Girls, Expert (all age categories) and Sport (all age categories).

The Venue:

Receiving's First Place for Best Bike Parks of 2014, the Silver Mountain Bike Park venue will make sure that the best of the best individuals and teams in North America will be crowned champions.