1. First select Settings > Network Settings
2. Then select Internet Connection Settings
3. Click Yes when you receive a warning that you will be disconnected from the Internet
4. Then select Custom and leave all settings as they are until you come to DNS settings. Select Manual
5. Input Primary DNS 188.8.131.52 & Secondary DNS 184.108.40.206
6. Then keep pressing the right button until you are offered to check connection. Go ahead and do the check and then save settings
7. Go on to restart the PS3
In order to install US apps on your PS3 you need a US PSN account. Simply go to http://us.playstation.com/psn/ and create a US PSN account. Once done use the US account with the Playstation store and search for the apps and install the app. From then on you are good to go.
Please note that if you have already have the us application installed you might need to reset settings in the app. This is done by holding down Start and Select while opening the app.
First step of troubleshooting should always be to restart device(s) and router. Then check your setup status in your SmartDNS dashboard.