Unless someone happens to have a lucky guess, we'll have to have more info that this. Many different trees could match what little description you give.

How would you judge that it "defin(i)tely looked like it was native"?

Any chance you could get a few good pictures (leaf, leaf arrangement, bark, etc)?

Not many trees/shrubs have clear bright orange fall color. Sugar maple is one and from my description it definately ain't sugar maple. Not fothergilla either the leaf shape is wrong. Leaf shape looked smallish and narrow oval kind of like a sourwood. If you put a sourwood in miniture made the leaves smaller and gave it bright, clear orange fall color. That is how I would describe it.

I assume native because I saw many of them and several locations. Roadside and in the woods. Not planted in peoples yards. Could be wrong.

They are off the road so unless I park and walk out into the field so I'm not going to get a close look. The feel of the small tree/shrub is light and airy.

My guess would either be sumac which looks awesome this time of year or maybe sassafras - although our sassafras trees look much more red than orange.