There has always been population migration... Maybe it is a bit harsh to call these migrations an invasion, but, at least in Europe, with the increased population migration from Africa in the last 10 years, one gets the impression that it is an invasion. For America, I am sure that the pressure from the south is also present every day.
Those people who emigrate from their countries certainly do not want anything bad for the country they are coming to, they are just looking for their place under the sun, but the fact is that they bring with them their religion, culture, customs, which were not everyday in the countries they settle... And thus one gets the impression of violent promotion of some new customs of a large number of new inhabitants.
An example of a country that is against accepting migrants is Hungary. We will see in the years to come, how good the raising of high fences was for their system (economy, demography, population...).