Can my empolyer change me from salaried to hourly pay

In a word, yes, unless it's prohibited by Union or an employment contract.

When the conditions of your employment change SUBSTANTIALLY you can resign and file for Unemployment. That doesn't mean you will collect it, however.

What is the advantage to your employer of changing you from salary to hourly?

Unless you have a contract or unless it is protected by union or other agreement.

With that said, if you have been working a lot over 40 hours a week, you may prefer it. Since it may add money, depending on the amount they are gong to pay per hour.
Also they may try to keep you at 40 hours if they now have to pay over time.

After that, also if the job you did was or should actually be hourly, then they may have needed to change it to follow payroll rules.

Are you having issues with it.

Unless you have a contract or unless it is protected by union or other agreement.

With that said, if you have been working a lot over 40 hours a week, you may prefer it. Since it may add money, depending on the amount they are gong to pay per hour.
Also they may try to keep you at 40 hours if they now have to pay over time.

After that, also if the job you did was or should actually be hourly, then they may have needed to change it to follow payroll rules.

Are you having issues with it.