"Seppo" is rarely used in Australia today, it's an old bottom-of-barrel word most have never heard of. The neutral "Yank" is more common, but even that only pops up sometimes.

Guessing their comment attempts to expose hypocrisy of America's keenly supported overseas military activity in conflict with fiercely defended domestic free-speech and liberty principles. Deep down, most allies of America want America to defeat foreign adversaries and keep defending those liberties many of us share. In other words there's no hypocrisy, carry on!