<<Disclaimer: Verify this information before applying it to your situation.>>

Although I've never shipped stuff to South America, I've sent several
packages to New Zealand.

If your location is served by Global Priority Mail, it is a bargain for
packages under four pounds that fit in the standard envelope (same as the
larger Express or Priority Mail cardboard envelopes) and get there in less
than a week.  They handle larger packages too but, believe it or not,  the
price per pound is higher--or at least it was the last time I looked.
Obviously it's not a good deal for flours and other bulk items, but
worthwhile for specialty stuff.

Many companies do not ship overseas because it requires non-standard
handling like customs forms, etc.  However, those who make products for
special needs are much more likely to make the extra effort.

The other problem is currency.  Look for a company that takes credit
cards--assuming you have a card that can be cleared through US banks.
Otherwise you need to get a bank draft in US dollars which is an extra
effort and can be a considerable expense.

Barbara