Not necessarily.
The Western Roman Empire was invaded by a horde of Germans of various tribal affiliations in December, 405 A.D. The irruption was by organized bands consisting of tribal and clan groups, including entire families.
Quote:
"We have Nicaragua, soon we will have El Salvador, Guatemala, Honduras, Costa Rica, and Mexico. One day, tomorrow or five years or fifteen years from now, we're going to take 5 to 10 million Mexicans and they are going into Dallas, into El Paso, into Houston, into New Mexico, into San Diego, and each one will have embedded in his mind the idea of killing ten Americans."--Thomas Borge, Nicaragua Interior Minister as quoted in the Washington Times, March 27, 1985
Wasn't one of the problems with the Hun that the Romans gave them citizenship if they'd fight in the army so the Hun just moved on in and made themselves at home? Didn't the dilution of Roman Citizenship lead to the "Bread and Circuses" problem and ultimately to the dissolution of the Republic?
I really believe the right guy could come along and get elected Caesar right about now.
It's an invasion, any way you define it.