A thread started by SEW mod, mcanerin, named Should there be a Google USA? asks the question that many have been thinking about for years. The poll asks "Should Google.com and Google.us be different?" and there is currently a dead heat between option 1, "No. The .com is already the US version. Keep it that way." and option 2, "Google.us would be more relevent, The USA counts as a region too!"
Let's step back a bit. While reading the thread, I kept thinking to myself that the .com extension was pretty much designated for US based businesses or other businesses that wanted it. Not until relatively recently did the .us extension become a domain of choice for US based businesses. The .com, to many, symbolized a US operated (or serviced the US) business. So in a sense, the .com is really not "international" based but rather it is US based Google results.
Bill, bragadocchio, explains that "The .us tld has been around since sometime in 1988. The .com was from around three years earlier in 1985, as was the .uk."
The thread remains to be interesting, and I for one, would love to hear from a Google representative as to what they do specifically for the .com and what logic they used in this decision.