Honda offers the Acura CSX only in Canada, rebadged as a Honda is known as the 4 door sedan Civic is sold in the global market along side the Honda 5 door/hatch not sold in North America.
The Civic which has a the shorter front hood redesigned front clip and rear is sold only in Canada, Mexico, some South American, Caribbean markets and USA.
Honda sells the Acura brand in Canada, USA, Mexico, and China.
The way you phrased this makes it seem like you're saying the Civic is slightly smaller than the CSX. The CSX (being based on the Civic platform with minor changes cosmetically, to the interior, and a different drivetrain package), they are dimensionally identical.
Rephrase- Differentiating the Acura CSX from its mainstream North American counterpart Civic include a slightly longer nose
CSX/Global Civic sedan Length (mm) : 4544 (178.9 in)
Americas Civic sedan Length (mm) : 4504 (176.7 in )