Which nations in human history have successfully suppressed the massed incursions of "outsiders"?

The United States along with any other sovereign nation. A country must know who is in it. We have had orchestrated invasions under both Obama and Biden in my lifetime.

You’ve lived a VERY short life if you believe these “invasions” restricted to Obama & Biden.

And this country is VERY aware statistically of who’s here.

China’s great wall kept out the Mongols.

For how long?

@HP Well, I’m not old. Which others, if you don’t mind.

Immigration to Italy !

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

@RedDeerGuy1 and it was not only Mongols, but recurring threats from outlying lands and particularly the nomadic peoples from the vast grasslands of the steppe. The Mongols were ,as with us, one among many.

@SnipSnip Pick your President. The reality is that the United States is the relief valve for any major crisis South of us. This from a continent distinguished for political instability and frequent upheaval, not to mention the unrest on our own continent and the various islands.

I don’t see how most of these answers have anything to do with the question.
Samoa is still largely Samoan, but of course has been heavily influenced by outsider residents.

Tourists? American or French Samoa have a problem with a threat of mass migration? Aren’t Samoans citizens of this country and entitled to come here as they please? And the French Samoans have better living than us.