The falklands.
it was invaded, but the Argies got messed up trying, and there was no native population before british settlement.
Antarctica isn’t a country / sovereign nation though is it? It is some land that many governments cooperate to work on. It is a continent but not a country.
But if you fill out an online form ore even install an OS Antarctica is in the country list and it has an IDD code and on ofr the definitions in the dictionary is “a tract of land considered apart from any geographical or political limits; region; district.”
The moon, no one said it had to be on earth 
I don’t think you can say the moon is a
country/nation though
This was a crazy joke untill I really thought about it… easter island!
Can we count this as a invasion?
“In December 1862, Peruvian slave raiders struck Easter Island. Violent abductions continued for several months, eventually capturing or killing around 1500 men and women, about half of the island’s population.”
I was thinking the slavers were not really organised and this thing was happening globally. When they were contacted by colonies they were simply explorers who documented what they saw and nobody ever went back to invade as it was considered such a unique culture.