What if your US customer is not located in a major city like Houston or Atlanta but is headquartered in small regional city like Bentonville AR (Wal-Mart) or Fort Worth TX (Radio Shack). In that case you need to work out how often you need to be there and then decide if you should be based there.
My second piece of advice is, “Understand that you will also need to travel to customers around the US in order to maintain and grow your position in the US ”. Locating your US office near a major airport hub (e.g. Atlanta or Dallas/Fort Worth) provides access to multiple daily flights to take you to your customers. A direct flight can allow you to get to/from a meeting in another US city on the same day which minimizes overnight accommodation costs. That cost saving is important because at the end of the day your decision to set up a US office is not a question of where, but rather, “Where can I get the best return on my investment?”