Because EU server has a lot of problems, here is a program to switch from EU/US server easily with 1 click.
Extract into game folder (same where you have the lol.launcher.exe file) and run. Close the game before doing this. You don't need to download US version of LoL if you use this tool. Also it is possible to modify lol.properties manually in notepad but this tool makes it easy even if you are "noob".

Program link: http://www.leaguevideos.com/LoLLauncher.zip (Size: around 80 KB)
EXTRACT INTO LOL GAME FOLDER. You need .NET Framework version at least 2.0. (Already installed on all Windows 7)

To play on US server you need to make a new US (North America) account. On the US account you will start again at level 1. Your EU account will stay the same level and everything. You cannot use EU account on US server (and vice versa).

To create US account go here: http://signup.leagueoflegends.com/en/signup/index
Make sure it says North America under Region!!! Because by default it will say "Europe".

If you see "offline" for a server and you think it should say online, this program now also have a little patch that you can enable so the server will always report as online. If the server is really offline then it won't connect when you try to log in though.

SOURCE CODE: https://github.com/mrbrdo/LoLLauncher (C#.NET Visual Studio 2010)

Also check out the program sponsor site LeagueVideos at http://www.leaguevideos.com/

PS2: I am m4s3rexpl0d3r @ US servers u can add me if u want. I'm pretty low lvl cause I only play there when the EU servers don't work.

Also, if you use another program to do the same thing or you do it manually by changing files NOBODY CARES! So stop posting about that already. Use whatever program you want, if you don't like mine for whatever reason you don't need to cry about it here.

why i just downloaded eu lol and us lol and i can play both dont need to use things people give just download them and double click there link.

i get a error...

unable to find a version of runtime to this app

Just change the lol.properties file in the air folder.

Am i the only one for whom the us servers are down ?

Am I the only one for whom the us servers are unavailable ?