what do you mean? can you please explain?
Since you have a US account, any codes you use also need to be US codes.
You can't, for example, use an Online Pass code from an EU copy of RBS with your US account. RBS will play fine, but the code won't work unless you log in with an EU account.
You'll need to import a copy of RBS from the US and use the Online Pass from it to play online on a US account. Alternatively, you can pay the $10 on the US PSN Store for the Online Pass for an EU copy of RBS.