Amway,
Your question needs quite a bit of clarification. Google's geo preference works a bit differently than just .com vs. .us for the same /similar content.
So, if you use a .US outside of the US you are stating you want to target US customers. A .com is not country specific so it won't necessarily exclude any region, but if you are outside the US, with server outside the US and with no geo targeting input, and your customer is in the US, I would use a .US.
A .com is generally better for the US than a .us for the US customer, but for a different reason than Google.
If a US customer sees .US for one result and a similar result (different site) with .com, I believe that 8 times out of 10 they will take the .com because they are more comfortable with it.
I hope that helps.
Remember, if you are using the same or very similar content, be very careful with canonicalization, etc. when trying to use both.
Best,
Robert
