The best time to plant trees and shrubs is when they are dormant. For a maple tree, that would be during April, before the leaves begin to emerge. The root system is disturbed during transplant, and while it will take up some water from the soil, it will not function at 100%. It can take a month or two for the root system to recover, and during this period, any leaves or flowers present will suffer. Chances are, the tree will recover, and next year, it will green up in the spring and grow well. It is possible to successfully transplant trees and shrubs in the fall, as the growing season is ending, but before the ground is frozen. I have successfully transplanted blueberry shrubs around September 15, here in Madison, WI.

I agree with ericwi, it is probably just suffering from transplant shock. You may see any leaves that were mature when planted start to die back like in the picture.

The good news is that by planting it now, the tree will have a nice, long growth season to establish a strong root system before the fall and first freeze. A strong root system is what it needs to survive the cold, frozen, Midwest winters.

Next year, it should be just fine. If not, make sure to keep the receipt and the nursery (and even stores like Lowes or Home Depot - who's quality of trees is actually quite high), will replace it.