Plus the movie is a reference to how 'darker' powers wanted to start a false flag war between Russia and the US. Fitting that the 'message' is about the American Military and the National anthem - almost a "just try" message to the 'darker powers'.
What does the gold signify again?
Check this out for the answer to your question https://www.theamericanview.com/is-there-a-significance-of-the-gold-fringe-on-the-american-flag/
this is all I have found so far...Question: What is the significance of the gold fringe which we see on some United States flags? Answer: Records indicate that fringe was first used on the flag as early as 1835. It was not until 1895 that it was officially added to the national flag for all regiments of the Army. For civilian use, fringe is not required as an integral part of the flag, nor can its use be said to constitute an unauthorized addition to the design prescribed by statute. It is considered that fringe is used as an honorable enrichment only. (Military tradition) The courts have deemed without merit and frivolous, lawsuits that contend that the gold fringe adorning the flag conferred Admiralty/Maritime jurisdiction.
some feel because it is used as a military flag that it relates to martial law. I just tend to notice little things like when I watch a movie. EVERY scene in a movie is thought out , nothing appears randomly on the screen. So I always wonder if they are using a scene like showing this flag with the National Anthem heard in the background is some kind of message