There is no answer to this question.
All-mountain is one of the latest riding style category name, (I say category name because people had been riding like this for long time but naming this category and manufacturing specific bikes is pushing the hype) all bicycle company has an all-mountain specific model.
It is almost impossible to pick one because all-mountain is not a very precise definition it can lean towards XC or be more aggressive, easy on the climbs or just "can climb" but very fun on descents... so I can pick one according to MY riding style.
General definition for an all-mountain bike would be: 5"-6" front and rear travel on a pedal friendly platform
To name a few models: Giant Reign, Kona Coiler (or DAWG depend on rider style), Turner 6-pack (or 5-Spot ), Intense 5.5, Santa Cruz Nomad (or Heckler), Ellsworth Moment (or Epiphany), Banshee Pyre, Cannondale Prophet, Specialized Enduro.... and more...
I would pick the Ellsworth Epiphany or Banshee Pyre BUT thats according to my riding style AND MOST IMPORTANT personal match (one must test ride it before he buys)

BTW "In the USA" do you mean manufactured in the USA?