Nowhere in the article does it state that these methods can be used against US persons separate from other protections against surveillance on US persons, nor does it give the impression that this is special to US persons:

The agency’s success in defeating many of the privacy protections offered by encryption does not change the rules that prohibit the deliberate targeting of Americans’ e-mails or phone calls without a warrant.

Let's keep in mind the fact that an intelligence agency is built to gather intelligence on other governments/organizations and that often involves breaking other jurisdiction's rules.