According to conventional science the first modern homo sapien was born somewhere between 70,000 and 100,000 years ago. To simplify lets just take the mid point and call it 85,000 years ago.
The population of the planet reached one billion people in 1804 - 85,000 years for the population of the planet to reach one billion people. The population of the Earth has increased by more than four billion people in the last 50 years.
85,000 years to reach the first billion. 50 years to produce 4X that many. Most of the increase is coming from third world locations.
I mention this to point out why it's necessary for a developed country to severely limit immigration. Any country that doesn't will soon be overwhelmed with third world immigration.
People often make comparisons between the fall of the Roman Empire and current day America. But Rome never had to face the situation that exists in the world today. An influx of barbarians eventually broke down the Roman culture and its institutions. The quantity of barbarians in the world today will completely eat any country that doesn't limit their entry.
America is too far down the path of being eaten already. It's time to start backing up.
I would suggest, implicit in your argument, and I would say explicitly, that internal dynamics ALLOWS for and encourages such destructive immigration. It is the internal power brokers that allow the damage to benefit themselves. So, fundamentally, it is not the barbarians that are the problem, it is the people that open the doors for them.