At the end of the day it's going to be arbitrary. If you take a group of people and ask them what the rising sun flag represents, the majority response will be

At the end of the day it's going to be arbitrary. If you take a group of people and ask them what the rising sun flag represents, the majority response will be about WWII imperialist Japan. Which makes sense as they changed it immediately after their surrender in WWII. It legitimately is viewed like the nazi flag by the various Korean people I've talked to in Korea. The context also matters. Korea has plenty of swastikas. Specifically at shrines/temples and on the ground; not being flown as part of flags. "What about Y" is a weak argument to keep X flag. You could make that argument for basically any flag. To answer though, it's likely the US flag will be seen in a similar light once it's no longer a powerful hegemony. If the US had a flag that was only used during its "imperialist era" and a different modern one, one would have a stronger argument.