Let's look at a single example: Germany. From Wikipedia I learn "In 2015, 36% children under 5 years old [in Germany] had migrant background." There are 1.5 million Turkish nationals with legal residence in Germany. At 5.2% Islam is the 4th-most common religion in Wiki's list for Germany. ("No Religion" is in 1st place with 39% — maybe that's part of the reason they haven't descended into chaos like the U.S.)
So Jayjay is right. Whatever the reasons for U.S. dysfunction, diversity is not the main problem.
As recently as a decade ago, America was an inspiration to the rest of the world, a beacon of freedom. I ask all reading the thread, especially OP, to re-read the sonnet inscribed in the Statue of Liberty:
Emma Lazarus said:
Not like the brazen giant of Greek fame,
With conquering limbs astride from land to land;
Here at our sea-washed, sunset gates shall stand
A mighty woman with a torch, whose flame
Is the imprisoned lightning, and her name
Mother of Exiles. From her beacon-hand
Glows world-wide welcome; her mild eyes command
The air-bridged harbor that twin cities frame.
"Keep, ancient lands, your storied pomp!" cries she
With silent lips. "Give me your tired, your poor,
Your huddled masses yearning to breathe free,
The wretched refuse of your teeming shore.
Send these, the homeless, tempest-tost to me,
I lift my lamp beside the golden door!"
Time was when travelers like myself were proud to bear the blue passport of the U.S.A. By now, some of us are ashamed and pretend to be Canadian.
So no, "diversity" is NOT the problem. To the contrary
Diversity was once the Solution. I'll reveal the problem, but will hope that font size 5 is good enough. OP: Please use your browser's zoom function if you need to see this more clearly.
The U.S.A.'s problem is Stupidity.
In the United States, there are millions of Americans who do not want to take the Covid-19 vaccine because Bill Gates has put implants in the vaccines. If they get the vaccine, they will be brainwashed and forced to forget that the Jews and the Blacks killed Jesus. A huge number of Americans are outraged that the mainstream media ignores one of the biggest stories of our time: Hillary Clinton eats human babies for breakfast. Every single word that oozes out of the fetid pie-holes of would-be Presidents like Ted Cruz or Josh Hawley is a lie. I could go on, but with the bizarre ignorance of OP, I wonder
What's the point?
Hope this helps.