In my tentative years of watching Sci-Fi and other years studying Military technology and Geopolitics, it all goes down to one question, "What are the Aliens?" I mean, if they're hyperintelligent and hyperadapative, than you can probably kiss your ass good bye as if you aren't able to wipe them out in one swipe, they'd adapt. But if they're "human intelligent" but only possesses advanced technologies, than we have a chance as our brain powers are on par, the only difference would be what we have and what we do with it.
If an Alien attack happens to China (something tells me enslaving 1.3 billion people is more attractive than enslaving 300 million), and let me be clear, unless the Aliens in question don't have the technology to "spot" the highest tech location on Earth, they'd probably go for the most resource rich location, if it's raw materials, depends on what they want, but candidates would be: Southern Africa, India, Australia, U.S. and China. But, if it's humans they want, East Asia is the prime candidate, so I'll assume that:
1. The Aliens have similar brain chemistry as us
2. The Aliens have more advanced technologies than us
3. The Aliens are attacking to enslave us
4. China will be the first to be invaded
Aliens are not dumb, they usually aren't, unless they're some long-living species that are a tad slow (like that one episode of ST:TNG). So, unless military tactics evolve passed Sun Tzu's logic and the lessons learned from those 2 latter millenniums of warfare, they'd probably start their invasion with a classic American Shock N' Awe campaign, I'm guessing, massed EMP attacks and a Mass driver campaign (I.E. towing small meteoroids and crashing them on select locals). To be frank, chances are, even the hardest bunkers, will be destroyed, so the Nuclear Option is down.
Then comes the Air Dominance campaign. Assuming their Carbon-based lifeforms and require Oxygen like we do, they probably prepared Aircrafts capable of Endoatmospheric and Exoatmospheric flight, i.e., eject off the Mothership's bay, soother along into the Atmosphere, and preform like a well played dogfighter. Sci-fi theorists who think that Aliens will use Lasers or Plasma beams are idiots. They'd probably use high-performance, long range missiles (because they are autonomous and can track targets, unlike dumb lasers that go in one direction), but granted, they'd probably use high-powered lasers for Ground attack or Dogfighting.
In my scenario, chances are, every plane on Earth, that is flying, F-22s, T-50s, J-20s, etc, will get shot down at ~500 km away. Not even a chance. Once they've cleared the skies, they'd launch strike crafts and then destroy strategic ground and naval locals. Most notably, even the mighty USN's 100,000 tonne investment will be sunk without much of a challenge, Submarines, even the quietest ones, will be toppled over by bombardments from above. In my scenario, the only thing left is Man and Army. We can discuss tactics later, but it'd be a hard fight.