Let me start off by saying this: i have not played or bought COD: Ghosts and i never will. Modern Warfare 3 and Black Ops 2 was the end of Call Of Duty for me in terms of buying the games themselves(i still play them). With that said, i haven't seen the entire story, and feel free to correct me on anything.
1. America's defenses being "weakened".
So from what i've heard, the game starts off with an into that would imply that America's Military has been weakened or even crippled, yet apparently throughout the story America appears to have a huge arsenal of weapons at it's disposal, such as ships,missile launchers, Nukes, ETC. So where does the part where the army has been weakened come in?
2. Since when has South America been a threat to North America?
Alright this is beyond stupid, since WHEN has South America has the ability to attack North America OR hack into their computers? Why not choose someone who actually DOES have the power like China or maybe even Russia.
3. Taking away America's Orbital missile launcher
And Who in in the right mind thinks it's a good idea to give America an Orbital Missile Launcher Exactly? Even if South America hacked into it, they would do it to protect themselves from being shot by North America. You know what? South America should have an orbital Missile Launcher to use against the U.S. and stop it from blowing up the earth.
4. America using the Orbital Missile Launcher.
And this is why we can't have anything nice, now isn't it? America constructs a device that can kill thousands of people, South America hacks it to protect themselves (i would assume), and America regain control of it and kill Innocent people. Way to make America look like the bad guys eh?
So, there's some pretty shocking news you may be interested in hearing;
IT'S A F*CKING VIDEO GAME.
Get over yourself. You're worse than one of those annoying kids at the movie theater who sit there and say "Oh thats so fake, if that were real it wouldn't work".
You obviously didn't pay attention to the story. This game takes place well into the future where there's a group called the Federation who takes over South America after controlling to worlds oil production in the Middle East. ODIN is not an orbital missile launcher. It's just a really heavy rod that uses the rate of gravity to accelerate down to Earth causing a giant shockwave. This is a very plausible defense system as it's dead simple to implement.
Reality check 1: A video game is not meant to mimic real life.
Reality check 2: Yes China has the capability to take on the US in terms of man power. Issue lies in getting all of those men over here, they don't have the equipment to do it.
Reality check 3: This happens in the future and it is very plausible that South America could suddenly become powerful (all they'd need to do is unite and bring in all of the cartels) in said future.
Reality check 4: THIS IS A VIDEO GAME.