OK, from what you say you have ADSL. In other words internet via the phone line wire, but not a dial up modem.
Generally just as fast as cable. With cable it doesn't matter how far away from the exchange you are but everyone is on the same cable. The more peeps torrenting and DLing pr0n, the more it degrades the cables performance.
With ADSL it doesn't matter, the pair of wires are yours back to the exchange. But the further you are from the exchange the less the performance.
What is killing you is the fact that you are connected to the modem via wireless. The modem should have an ethernet port, as should your laptop. Connect directly to the modem with a network cable (blue usually, with RJ connectors each end), and remember to disable the wireless on the laptop.
Give us the specs on your laptop. You should adjust your video settings down depending on your gear. If the laptop is struggling, turn off some crap. AA, dynamic lighting, shading, whatever. There are console commands to turn off brass ejection and decals which will give you a few more FPS.
Second, don't have ANY other programs running in the background. Shut down the browser. Go CTR ALT DEL and check the Applications tab. It should only have COD4. Make sure there are no stupid processes like printer apps and webcam crap. And if other users are on in the household this will affect performance. Give us a screenshot of your processes tab if you don't know what to turn off.
Like I said earlier (I think your intro) the best ping you will expect from the USA is a bit over 200ms. The signal only travel at the speed of light. 186 thousand miles a second. To the S1 server and back is about 24 thousand miles. That's about 130 milliseconds before you add in any latency from all the routing points.