I have a single handle American Standards and when I turn handle to Hot Cold water comes out. I have changed the cartridge but same outcome. What else could it be?

When you had the valve apart did you turn the water back on to flush out the supplies?
You should have a strong hot water flow when you do. Good luck, Tom

When you had the valve apart did you turn the water back on to flush out the supplies?
You should have a strong hot water flow when you do. Good luck, Tom
Well I had someone change the value but now I have no water pressure when the hot eater is on even if I turn the cold water to shower off. I am going to have them remove the value again and then flush line and try again.

If flushing the valve doesn't fix the issue but you find you have good pressure from hot and cold BUT the hot isn't hot then check the TEMPERATURE LIMITING DEVICE... probably set too low!

Mark