The Grand Ayatollah Sistani answered a question about performing Salaat Imam Zaman (AJ).
Question: Can Salaat Imam Zaman (AJ) be performed in congregation or in a group?
The Grand Ayatollah Sistani: It (Salaat Imam Zaman (AJ)) is not allowed in congregation but there is no problem in a group.
Source: PERSIAN SHAFAQNA
What advice does Ayatollah Khomenehie give to the Muslims in America?
Concise answer
Asalaamu Alaikum,
Other than the topics which he has conveyed in his public announcements (which are available on his website[1]) the Supreme Leader has not expressed anything else in particular.