The United States of America is the worlds largest and most competitive market for Internet bandwith. Allmost all Tier 1 networks (networks that don't pay for peering with any other network) are US companies. So yes, 'all other things being equal', the US is the best place to set up a web farm.
However, that should be less important to you than daily management and maintenance. If your service is down, it doesn't matter to the customer how fast he gets the timeout. :-)
You could co-locate your equipment to the US, and set up a really good remote monitoring / access infrastructure, via a VPN and KVM over IP, or out-of-band KVM or console servers.
If you live in a location that has good global connectivity, say all of North America and Western Europe, many places on the Pacific Rim, then you could also just locate your servers locally, and use a CDN to mask some of the network latency for other regions.
In fact a CDN is always a good idea for a global website, no matter where the servers are.