I can see blacks and women simply running away from the line of action and blacks selling their equipment to the black market for some ganja. They can do it confidently with the knowledge that they'll face no punishment for doing so. It's racist to discipline precious blacks.

Blacks suffer the same consequences and go through the same military training as whites, the ones that you imagine would do this are weeded out beforehand. Blacks didn't do this in WW2 either. Here's one example:

In the midst of the Battle of the Bulge in December 1944, General Eisenhower was severely short of replacement troops for existing all-white companies. Consequently, he made the decision to allow 2000 black servicemen volunteers to serve in segregated platoons under the command of white lieutenants to replenish these companies.[53] These platoons would serve with distinction and, according to an Army survey in the summer of 1945, 84% were ranked "very well" and 16% were ranked "fairly well". No black platoon received a ranking of "poor" by those white officers or white soldiers that fought with them.

https://en.wikipedia.org/wiki/Military_history_of_African_Americans

The U.S military continues to maintain dominance without having actual boots on the ground. Just having the lion's share of aircraft carriers or assassinating foreign commanders with predator drones ensures the U.S can never be played with.

Americas aircraft carriers are known to be vulnerable to massed anti-ship missiles. This vulnerability increased after the development of the DF-21 missile by China. Their vulnerability became even more pronounced after the development of the 3M22 Zircon missile by Russia. Andrei Martyanov wrote an article about this.

Aircraft carriers are still valuable for projecting power around the world, but their vulnerability to supersonic anti-ship missiles limits their use against peer opponents.

Remember Qasem Soleimani? America took him out with a single missile and Iran couldn't do anything but cry. If they threatened an actual war, the U.S would wipe them off the face of the earth.

And thats the problem in its essence. The U.S. military can fight small wars with airstrikes and special forces, and they can fight nuclear wars, but they really have no capability in between those two extremes. They cannot really fight a conventional war against peer opponents like Russia, China, or even Iran. The U.S. military has degraded in its capabilitys since the Gulf war: The technology is better, but the culture is worse.

America has been around since 1776 and defeated every empire that crossed them. Britain, Spain, Germany, USSR. All destroyed. They're not called "back to back world war champs" for nothing.

In both world wars, Germany had already been heavily battered by the other powers before America entered the fighting. And they never actually fought against the Soviet Union: They merely outlasted them.