I vaguely remember this thread from 12 years back. I would agree that the flags were deliberately omitted. No doubt the US flag issue was part of the decision, though I have been to many assemblies where a US flag was draped up somewhere and nobody paid much attention to it.
The video though would be intended for a worldwide audience, where the majority of JWs nowadays are not in the US. So I wonder if the omission of the flags has more to do with appealing to non-US viewers than with the JW flag issue.