In Italy the "America" is the USA.
Of course we know that the America is the whole continent, but "Andare in America" always mean go to the USA.
If we go in Canada we say "Vado in Canada", or "Vado in Messico" for the Mexico or "Vado in Brasile" for the Brasil.
You know "Tu vuo' fa' l'Americano"? :-)))
As far as I can tell, the Italian word “America” actually means “the Americas”, not the United States; unlike the English word, which is more commonly used for the United States even though it shouldn’t be.
If so, then ideally this should be translated as “Her sister does not go to the Americas.” (not currently accepted, but should be even if it does not become the main translation).
Well, yes and no. Yes, it is a Latin form of this preposition, but it is also an Italian version. If "a" is followed by another "a" word (and in rare cases, this can happen with other vowels in conversation, from what I've heard), it becomes "ad", so the speaker can easily elide between the two words.
So if I lived in Arezzo (a city in Tuscany), I'd say, "Vivo ad Arezzo."
There's a huge difference between "goes" and "is going"
"Her sister does not go to America" connotes her sister shunning all travel to America, akin to "Her sister refuses to go to America". "is going" OTOH (On The Other Hand) simply means she has an up-coming trip to America scheduled. Also, "is going" would rarely and probably never be used to describe someone in the process of "going", because is also connotes "not having departed yet". And usually, you'd add something to "is travelling" like "as we speak" or "right now" or "at this moment".