If anyone wants to be added to or deleted from the ping list, let me know.
Mathematically, the probability is other advance civilizations should exist, though that chance is infinitesimally small.
IF aliens are here, the tech required for that visit is not generations away from what we have, it millennia away. There would be nothing any country could do to ‘defend’ against them. No more so than a dog could defeat an F-16.