Hello PMC!

I've been getting into banner more and more lately and have even opened a banner shop on a server I play on often that specializes in National Banners (Nation Flags). I aim to make and display every banner as customs and rules of that country dictate. Being an American citizen I exercise this same level of detail and accuracy with the Star Spangled Banner. I have seen both online and in game the most disgusting and twisted ways of making the American Flag that I have literally become ill. First off, this is not an opinion. We Americans take great pride in our nation and the American flag is a symbol of everything our country was, is, and ever will be. Making an incorrect American flag is not just wrong, but disrespectful. So I am going to go over how to make a correct American flag and display tips for in game. If anyone sees something they think is wrong please politely comment and I will check it and fix if needed.

How to make the Banner

The technical term for the American flag is as follows:
Red Banner
White Paly
Blue Chief Dexter Canton

This is a link to banner builder that shows the correct flag:
http://www.needcoolshoes.com/banner?=bapBeC

You can also reinforce the layers to make the lines more solid like this:
http://www.needcoolshoes.com/banner?=bapBpBpBeCeCeC

Both are correctly made its just more of a styling preference. Some people will replace Red with Pink and Blue with Light Blue to make a "distressed look" This is a gray area. According to the U.S. Flag Code:

"When a flag is so tattered that it no longer fits to serve as a symbol of the United States, it should be destroyed in a dignified manner, preferably by burning."

Meaning a flag that has been damaged should not be flown and should be respectfully removed and destroyed.

Common mistakes

The first and most common mistake is the placement of the Union, the blue field where the 50 stars are. When making your banner you should have a Blue Chief DEXTER Canton not a SINSTER Canton which is a common mistake in Minecraft and real life. According to the U.S. Flag Code:

"When the flag is displayed against a wall vertically or horizontally, its union (stars) should be at the top, to the flag's own right, and to the observer's left."

This is important and many people believe the vertical flag (the kind displayed on a flag pole) can just be turned 90 degrees to fit a Minecraft banner when this is not true.

The second most common mistake when making an American Flag banner is to start with a WHITE banner and add a RED Paly. While the flag does have red and white stripes this design makes the outer striped white not red. On the actual American flag with 13 stripes the 1st and 13th stripe (the outer stripes) are red. As previously stated you must start with a RED banner and add a WHITE Paly.

I did see in one YouTube video that the banner was made so the Union was at the bottom which can be viewed as disrespectful. As U.S. Flag Code states:

"The flag should never be displayed with the union (the starred blue union in the Canton) down, except as a signal of dire distress in instances of extreme danger to life or property."

Note:
When making banners that are meant to resemble the flags of nations please make sure you do some research on how the flag is to be displayed vertically so you know how to craft a correct banner. This is out of respect for that nation and it citizens. This is highly suggested when making banners that will be publicly displayed on servers where players of that nationality may see them.

Thank you for reading and happy banner making!

Quotes on U.S. Flag Code may not be exact word for word. They were obtained here:
https://en.wikipedia.org/wiki/United_States_Flag_Code