The Time Lines of Earth are Galactically controlled

Why?

Because our ancestors blew up Maldek (now the asteroid belt) 65 million years ago with nuclear weapons. Because of this the Galaxy doesn't trust humans who are descended from Maldek and Mars humanoids. So, though we live on this planet the Galaxy controls all our timelines.

What this actually means is we have governments but don't control the ultimate decisions of what actually happens on our timelines. The Galaxy decides this in the end. However, all governments of earth help in various ways with this in co-operation with the Galactic Government. Because Earth Governments don't want all life on earth to go extinct either and have the planet permanently blown out of existence like our ancestors blew up Maldek. A piece of this planet (an asteroid) hit earth 65 million years ago and made all large dinosaurs extinct on land when it hit in the gulf of Mexico which created the Gulf of Mexico.

We won't be allowed to permanently blow up a planet like our ancestors did before. So, whenever humans have blown up earth since 1945 time has been changed back to what we are experiencing now.

There is no conflict between Earth and the Galaxy. There is only co-operation.