FAR part 61.56 ( [U.S.]Flight Review ) requires a U.S.flight review for anyone operating an "N" numbered airplane within the U.S. (when using a U.S. certificate/or U.S. certificate based on a foreign certificate), even if that person is current in another country for which he/she also holds a certificate.
See also, FAR 61.75 (Private pilot certificate issued on the basis of a foreign pilot license.)