Modern armies do not carry officially issued national flags into battle. There are three reasons for that:
One) Conspicously carrying a flag into battle attracts a lot of attention from the enemy and is highly dangerous.
Two) Modern armies usually fight in dispersed formations where only a small percentage of the troops in a unit would be aware of their unit's flag, so those flags would not be very effective in encouraging the soldiers to fight.
For those reasons most modern armies stopped carrying their flags into battle roughly about the period of 1880 to 1920.
Three) Officially issued military flags are the flags of the units they were issued to.
Each battalion or regiment has a flag called a color, except that some armies like the UK and USA armies have two colors per battalion or regiment. Those colors can have many different designs. Some are based on the national flag, some are based on the national coat of arms, and some are completely different from either.
Since the USA has two colors per regiment, a regiment will have both a national color with a design based on the national flag, and a regimental color based on the national coat of arms, which I consider to be a highly logical pattern.
Some armies, like the US army, also have flags of companies, smaller units within a regiment, which are called guidons.
And larger units that regiments may be grouped into, such as brigades, divisions, corps, field armies, etc. can have their unit flags.
https://en.wikipedia.org/wiki/Military_colours,_standards_and_guidons
Colors used to be carried into battle to inspire the troops, but that has been abandoned for over a century because of the dispersed formations of modern armies and the great danger to the color bearers. So the colors are seen only in military ceremonies. However, it is possible that the colors are taken in military expeditions in the regimental headquarters baggage.
Soldiers often carry small flags of their country in their personal or unit baggage and fly them when they capture an enemy position.
The flags in the photo have different numbers of stripes than would be found in regulation national colors, or in the 1945 national flag (the national flag always had 13 stripes, except fora few years when it had 15). So I find it hard to believe that the flags are US national colors or intended to be US national flags.
I note that colors are usually made of natural or artifical silk, and usually have fringes, and cords ending in tassles. Colors are not run up on flag poles but attached to spear-like staffs, which usually have spearheads.
The flags in the photos are carried on staffs but don't look much like colors otherwise.
The soldiers in the photo are identified as members of the 45th Dvision, 7th US army.
The photos show two flags which seem to have very similar or identical patterns. I don't see any writing on the flags which might indicate that they were flags of military units.
I think that you found an interesting flag identification problem. If nobody here can answer it, you might want to ask at the vexilology subreddit.
https://www.reddit.com/r/vexillology/
