Are the wasteland deathclaws we know and love the deathclaws used by the US Army in combat, or a result of fev virus? Do we know what reptile besides the Jackson chameleon was used to create deathclaws?

There were created as weapons of War. I can't remember if they were used in China or not but I think it's most likely they were.

"Deathclaws were originally created to replace humans during close-combat search-and-destroy missions. They were derived from mixed animal stock and then refined by the Master, using genetic manipulation. The resulting creature is almost unbelievably fast and powerful." Page 27 Official FO2 S & S.

Wait a sec, what's that supposed to mean? It's talking about replacing humans in close combat indicating usage in the army then it says that they were "refined by the Master". Which Master are we talking about?

The Master from Fallout 1. Deathclaws were a pre-war creation but then the Master (Richard Grey) did his own experiments on them.

Edit: But to say all Deathclaws we have encountered in the series so far, are those that came from the Masters experiments would be wrong IMO.

Maybe the intention in the first game was for the type of Deathclaws we see in the Core Region to be the Master's strain. That would explain why the Deathclaws in Tactics were different. They could've come from the original strain. It could've been intended for the hairy, more intelligent Deathclaws to be the more common strain around the world because they were created before the Master came along.

Obviously, this isn't canon because Bethesda used the original Deathclaws in Fallout 3, but maybe interplay intended for these to be specific to the core region. Just a thought.

It is my understanding that the devs of Fallout orginally wanted more then one type of Deathclaw, including hairy ones. But the graphics weren't that great so they not nixed from the game. Not sure if that is true or not. But that could be possible yes.

My theory on the Tactics deathclaws is that they were created to fight in colder areas such as Alaska or the Himalayas.