These conspiracy theories are spread about to alarm people, and misinform. They are also potentially dangerous. Sadly, some people do become alarmed by them. Take a step back. Consider what it is you are fearful of and do some research (not just social media Facebook type research, either), apply some logic.
For example, an emergency alert trial makes perfect sense, given severe weather events and fires etc are increasing due to climate change - forewarned is forearmed. Many other countries already have such a warning system in place.
Asteroids always have and always will, on occasion, come quite close to Earth.
Solar events have been happening since the universe evolved and will continue to do so.
Space scientists/nasa will always be keeping an eye on asteroids, meteors and space debris we’ve created and their potential to cause damage on earth, therefore it makes sense to be developing and using technology to steer them off course if this is possible. (I don’t know, I’m no expert in that field). However, asteroids, meteors etc have, on occasion, hit earth - we have evidence of this, but earth still sustains life.
Nuclear war has always been a possibility since the development of nuclear weapons, however, logic would tell us that it would be illogical to go down that path as it would wipe humanity and most living creatures on this planet out - so, in effect, no winners.
The weird balloons? Possibly weather balloons, possibly spy balloons - all countries spy on each other to some degree.
Aliens? Hardly. I think if there were any, they’d see what we’re like and avoid us.