Written english vs spoken english

So you're saying that usally to give some news you(an american) wouldn't use the present perfect, right?

Huevos

The difference between the simple past and the present perfect is just a slight "Sss" sound. "somebody shot the president" versus "somebody's shot the president".

Hi Huevos
If you are a native speaker, then I'm sure you also realize that a native speaker will understand whether that 'sss' sound is there or not. In other words, a native speaker knows whether someone is saying somebody's or somebody. What I'm saying is that in the scenario I gave, I think it is far more likely that an American will use the simple past tense.  There won't even be a slight hint of a 'sss' sound connected to the end of the word 'somebody' -- because it just won't be there.

As regards "I ate already", Americans commonly use the words already, yet, and just (for example) with the simple past tense -- especially in spoken English:

- Did you see that movie yet?
- I just saw that movie.
- I already saw that movie./I saw that movie already.

Naturally, we use already, yet, and just with the present perfect as well.

Yankee

In other words, a native speaker knows whether someone is saying somebody's or somebody. What I'm saying is that in the scenario I gave, I think it is far more likely that an American will use the simple past tense.  There won't even be a slight hint of a 'sss' sound connected to the end of the word 'somebody'

I think non-natives make too much of a big deal of this. If I were to say to you "Somebody's shot the president"or you were to say to me "Somebody shot the president" it is very unlikely either of us would conciously register it or find it unnatural, and certainly neither would look upon it as an error.What do you think?

Huevos

If I were to say to you "Somebody's shot the president"or you were to say to me "Somebody shot the president" it is very unlikely either of us would conciously register it or find it unnatural

That's just it, Huevos -- I think "Somebody's shot the president" would register immediately as different or atypical or possibly even "wrong".  That is precisely the reason I gave that example.   I would be willing to bet that there would be more than just a few (non-English-teacher) Americans who, if asked directly, would actually go so far as to claim that "Somebody's shot the president!" is wrong. 

Yes, there are by far many more similarities than differences between BE and AmE.  Nevertheless, the differences are there.