Here is a super awful cell phone picture of the tree.

If the root/soil mass can be lifted from the pot intact, I'd lift the plant, tease out any roots at the perimeter and bottom of the root mass, then give them a bit of a prune with a sharp pair of scissors. Then tease out a LITTLE more soil from the root mass and pot up a size. Keep the plant in the shade for a week or so. Keep the soil damp, but not wet. Don't fertilize until you see the plant pushing new growth.

Al

The one thing I'd do is put it into a wider, if not necessarily shallower pot... maple roots like to spread sideways, not so much down.

Roots are opportunists. Species with a reputation for shallow root systems in situ will happily colonize the entire soil mass of even the deepest container if the soil has a favorable ratio of air:water.

In my native state, maple trees will have up to 90% of their fine feeder roots in the upper 4-6" of the soil. Later, during the dry days of summer, up to 90% of the fine rootage will be found below the 18" mark.

I had some hunting acreage on the Lake Huron shore that was very low, so low that even in summer you could dig a 6" hole and it would fill with water. The ground was wooded with about 2/3 maple and the rest mostly ash. The 160 acre parcel kept 4 families in firewood cutting only the blow-downs that occurred every time there was any significant wind - this, because the roots were right AT the surface and couldn't grow below the 6" mark. Containers are the same. Put a maple in a soggy soil and its roots will grow only above the PWT mark. Put it in a well aerated soil and - no problems.

Al

Holy cow, thank you for all of the info. This has been really helpful! I'll let you know how repotting goes,

Don't go crazy with how much rootage you remove. Your aim is to trim enough roots so the plant's chemical messengers tell the plant it needs to concentrate on root growth, which will be followed by a strong growth spurt. Remove too many roots while the plant is in leaf and it will defoliate - not something you want to deal with - especially when your tree is in such an early stage of development. The action you take should be thought of and performed as much closer to potting up than a full repot.

Al