Why would you need an American server? Well for one thing you may have found that you get blocked from accessing lot's of US only content. The method these sites use is they look at the location of your IP address when you connect.
This is assigned by your ISP and you can't change it. But if you use a USA proxy server then you can hide your real address and access whatever you like. It's quick and simple just watch the video and see how easy it is to access USA only content.
There are things you need to be careful about when using any proxy though, speed is essential especially if you want to stream or download large amounts of data. Also remember when you surf through a proxy all your browsing is being routed through this connection, never visit banking or secure sites through an untrusted proxy or VPN.