Let's say you get a device, or perhaps a biological agent, or maybe even a weirdly specific wizard-wand. It has one function. If you use it, all the non-native species in your country would be gone. Would you use it? And if you're on the fence, what conditions would sway you either way?
The first thing to consider would be the method by which they would "be gone." A clean disappearance is probably the worst option. As unpleasant as a plague of dead animals and plants would be, if they died, at least their material would still be in the ecosystem. If every member of a non-native species simply vanished, it would make for a lot of vanished biomass that could never be recovered. Obviously, though, an instant death for every non-native animal would be both heart-wrenching and a logistical problem. The ideal situation would be a slow phase-out, with non-native species no longer being able to reproduce and dying off over time.
Although the gradual phase-out would take a couple of decades to complete, it would also present massive problems. There would probably be quite a bit of starvation. People in America complain that too much of our food and housing materials are made of corn, but at least corn does grow in the Americas. Cows, pigs, quite a few species of wheat, and the all-American apple pie would disappear. Even recipes that aren't meat-based would have to be re-thought. Most recipes, when they call for "eggs," assume the eggs will be from chickens. Even a box mix of cake would have to be re-jiggered if we had to start using duck or turkey eggs. Then again, at least Americans could indulge in tomato sauce, potato pancakes, and cornbread. Europeans would be deprived of the lot.
Then there's the problem of figuring out what would evolve into the niches that the formerly-invasive species occupied. Many species now live on resources that native species once consumed before they were hunted to near or total extinction. Cows graze on land that used to be filled with bison. Starlings flock by the million through skies that were once occupied by the American passenger pigeon (and some say that the passenger pigeon moved into the niche left behind by other species of birds when they were wiped out). Getting rid of a non-native species sounds good, until we find out that a native species is even more pernicious when it moves into those open niches.
Still, despite all the problems, wouldn't it be interesting to see what different nations — or counties, or continents — could do with their native resources? And wouldn't it be interesting, when traveling, to see true and fundamental differences, from food, to wildlife, to pets, in every nation?
Then again, I think I might have to move to Egypt, Syria, or Cyprus — the nations that would manage to keep the domestic cat.
Top Image: Ameen Al-Ghetta