Merge and Center

Hello, I have attached a sample file to help explain.

I want to merge and center all the cells in column A that correspond to that states cities without having to go line by line. Is there a way to do this automatically?

EX: I want cells A2:A4, A5:A7, A8:A9, A11:A12, and A13:A15 to merge and center.

Maybe an if macro? I need some help lol

The reason is because i have multiple workbooks similar to this that are 50,000+ lines and going line by line would take a week.

Thanks in advance!!!!!!!!!