When implementing something via the Editor, the best place to start is always with an existing mechanism that already does something similar. So let's start with the Berserk edge, which adds +2 to Fighting (among other things).
Go to the Edge tab in the Editor and create a new edge as a COPY of Berserk. Take a look at the Eval Script and you'll see the line below, which adds +2 to the Fighting skill and attributes it to the "Berserk" edge.
Code:
perform #traitroll[skFighting,+,2,"Berserk"]
Also take note of the timing of the Eval Script, since you'll generally want to use the same timing for similar effects of your own. In this case, it's Pre-Traits/5000.
For the new thing you're adding for your custom dataset, you'll need to add an Eval Script with the same timing as above and a similar line of code. In your case, you'll want to change the "2" to a "1" and attribute the bonus to "USA" or something.
Hmmm. After re-reading your post right now, I may be misunderstanding what you're trying to accomplish, but I'm not sure. If you actually want to apply a +1 to the die type, then take a look at the "Undead" racial ability as an example (there are numerous others as well). In this case, "traitadjust" is used instead of "traitroll", but everything else is the same. So if you want to increase the die type, just use "traitadjust" instead and you should be good to go.
The one thing that isn't handled above is that neither of these methods automatically confers the Fighting skill to the character. The skill still needs to be added by the user. If the skill should be automatically conferred, then you'll need to bootstrap the skill to the character. This is accomplished via the Editor by clicking on the Bootstraps button and then automatically adding the "skFighting" skill to the character whenever the ability that gives the bonus is selected.
Hope this helps...