I am from Atlanta (Georgia)
You can say "Soy de Atlanta, Georgia".
"Soy de México" means "I am from Mexico".
Soy is used for nationality. I am from Spain
soy de... means: I am from... literally: "I am of..."
Yo soy de Portugal means 'I am from Portugal.'
i am from...
If by America you mean USA Soy de Estados unidos if you mean the continent soy de America
I am from here(abouts)
I am from Venezuela
It means: Where am I from? You are asking yourself what is your own origin or from what country are you.
No soy de Milano would translate into something along the lines of "I am not from Milano".
Soy de la in English means I am of. Ex. I am of Spanish heritage. (Soy de la Spanish heritage.)