By the end of 2017 I got my first performance review, in the letter they specified that I can only receive my new salary once I had evidence to obtain a certification on my field of expertise.
This is absolutely allowed. My job required that I earned a specific certificate within 6 months of starting it.
Because of various reasons (work load being the main one) I was unable to study and get such certification, therefore I stuck with my same salary all of 2018. By the end of my next review they basically sent me the same letter with same salary offered in 2017 again conditioned to a certification.
You shouldn’t expect to receive a different salary until you earn that certificate. You might want to ask what programs your company offers to help their employees earn the certificate in question.
My employer allowed my to study for the exam, paid for the exam, and pays for the recurring costs to keep the certificate that I was required to earn.
Your employer could also make it required at any point if they wanted. Typically, since it’s expensive to hire and train employees, they would give you time to earn the certificate (but that isn’t guaranteed).
I would appreciate if anyone can tell me if this is a common practice in the US.
This is common practice in many countries including the U.S.A