Sick Maple tree

[Knotthead]

This is the second summer our maple next to the driveway hasn't filled in. I think it was worse last year but she is certainly not feeling the best. Over the winter I thinned it some and before I go butchering again I was wondering if anyone has seen this before or has some best practices? It sure is in a nice spot and I'd hate for it to die and need to take it down. We've been at the property for 6 years. The only things I can think of that I may have done to contribute to its sickness are the following:
1- when we first moved in all the trees in the yard were like shrubs. I aggressively trimmed so I could actually mow around the darn things
2- I push snow towards this tree over winter
3- I had 15 yards of topsoil dumped 15 feet from the stump which was there for about 4 months
4- We live on a hill adjacent to an 80 acre corn/bean field.

Anyone know what this is called? Any suggestions to bring her back around?

 

[Raintree]

First guess would be a root collar disorder.
At 60-70% loss of canopy it's best to remove. Secondary pathogens will take advantage of the weakened state of your maple. If you must try and recover what is left of your tree. Remove the hostas carefully excavate the root collar then post pictures of the stump area.

 

[Knotthead]

The hostas use to go all around but the north side were devoured by white trails. I'm not sure how much excavation your looking for. I love trees but have a lot to learn. Thanks again for the education and help!

 

[Raintree]

That side of the stump looks good, it's also the side with most of the green leaves. If there is a problem it's on the opposite weakest side hidden by the hostas.

 

[Knotthead]

That side of the stump looks good, it's also the side with most of the green leaves. If there is a problem it's on the opposite weakest side hidden by the hostas.

Finally got around to digging out the hostas. Here the stump today, I'm not sure if the roots you see are from the hostas or the maple. Any insight is greatly appreciated.

 

[Raintree]

Brush or hose away the soil from the stump area. Look for a root similar to the above picture.