It should be "A world government." Or "a one government world."
This is all about connotation again; remember that there is more than one kind of meaning. Your choice of words tells us how you feel about what you're talking about. People want to start the phrase with "one" because their focus is on the harmony they expect to blanket the earth if we don't have multiple governments constantly competing and disagreeing with each other. And they don't want to reverse "world" and "government" because that requires an extra syllable (not to mention a hyphen in print): "A one-government world." It loses its forcefulness.
Someone's walking on my grave.
That's not nonsense. It's just a way of saying that under the conditions you currently perceive, you feel like your death is imminent.
Don't look at me in that tone of voice.
That's just silly. People are allowed to be silly. In fact I encourage it.
I was literally glued to the edge of my seat.
Oh don't get me started on that one. People have co-opted "literally" to mean "not quite literally."
That's just a simile. Doornails are obviously dead, so if someone is "dead as a doornail" it means you don't have to take their pulse to make sure.
Oh god! Oh GOD!!! OH GOD!!!!! OH GOD!!!!!!! OHhhhhhh GOD!
Anglophones are an irreverent culture, especially Americans. Some of our most common epithets would be regarded as blasphemy in other societies.
I'm riding shotgun! - I don't consider this 1 of the worst but it's a shame so many don't know where it came from.
There hasn't been a stagecoach in operation in the anglophone world for at least three generations, and therefore no roadside bandits, so it's not remarkable that people don't know why the seat next to the driver in a vehicle was once reserved for the guy with the shotgun. Still, "western" movies were popular up until 25-30 years ago so people of my generation are quite familiar with the origin of the phrase.
Hold your head up high. -- She has her nose in the air.
Those aren't nonsense. People who are ashamed or timid tend to look downward. Which leads to the phenomenon of snooty people holding their heads so high that they're looking over our heads.
Only the guilty flee. -- The police wouldn't have arrested him if he wasn't guilty.
Those aren't "nonsense expressions" either. There are unfortunately quite a few people who believe that crap. Please don't lose the point of this thread.
Another simile, a perfectly proper and understandable statement. Not nonsense.
An exaggeration. Again, not nonsense.
That's a perfectly reasonable way of saying, "I'm so surprised that turned out to be false."
Please try to stay on topic here.