Not every trademark registered with the USPTO had to have been used in U.S. commerce prior to registration. The Madrid Protocol allows applicants to register a trademark in the U.S. based upon an international registration without having to show prior usage in the U.S.
If a pending trademark application has been rejected on the grounds of a likelihood of confusion over a Madrid Protocol U.S. registration, it may be worth investigating whether the blocking trademark has been used in the U.S. for the registered goods or services. If it can be proven that a Madrid owner has failed to use the mark in U.S. commerce for three consecutive years, then the trademark may be subject to cancellation for abandonment.
Foreign owners of U.S. registrations via the Madrid Protocol should take care to use the registered mark promptly after the U.S. registration date, and to avoid a 3-year consecutive period of non-use which would give rise to a legal presumption of abandonment. In particular, registration owners should not merely wait upon the sixth-year deadline under Section 8 or Section 71 to begin using the mark in U.S. commerce.