Make anything black and yellow in Pittsburgh and you'll sell a lot of it
The Rising Sun Flag
is considered offensive in East Asian countries, specifically in China and the Koreas, as it is considered to be associated with Japanese militarism and Japanese imperialism during World War II.It looks more interesting, I guess, than the current Japanese flag, and as such it gets used inappropriately on t-shirts and in ad campaigns (such as by the Chicago Cubs when Kosuke Fukudome joined them in 2008).
While many of the shirts---like the English, Italian, and Korean versions, for example---have the country's flag, others---like the Slovak, Ukranian, and Puerto Rican ones---have the country's shape or another easily-recognizable emblem. A typical yinzer reaction to anyone being upset by the shirt would be "well this ain't China or the Koreas". But considering how few Japanese visitors to and residents of Pittsburgh would by a "I'm a Japanese Steelers Fan" shirt to begin with, and how even fewer would wear one with this logo, Burgh Nation Tees might want to think about switching to something less controversial when they print the next batch.