I know that in the Caribbean we have to make sure that we use an US/EU card set up so that as the yachts travel from area to area they can keep cell service.
the 3g and 4g are the same frequencies that I deal with in US/ Carib/ and Eu so I would venture a guess that an US/ EU router will work in south America no problem.
as to the speed “bonding” when we try to use them simultaneously. the weaker service tends to drag the others down. (maybe the way I have been setting them up but for us that is the reality)