I have a good-sized (10" trunk 20-25' high) sugar maple next to the
street in front of my house. Last year it was very thin, leaf-wise,
and turned to fall color mid-August. By mid September it had dropped
all its leaves, way earlier than other trees in my Zone 5 neighborhood.

This year its even thinner leaf-wise! I called the village (who
maintains the trees in the parkway, the strip of grass next to the
street) mid-June and they sent a guy out. He said: "Yep, you've got
a problem, we're not sure what. We've scheduled a root inspection, it
might be root-bound."

Sugar maple is a very poor choice for that location. If I were running your
village, I would cut the tree down (the wood is valuable) and replace it with
something more suitable, like a linden. Otherwise it will probably continue to
die a slow agonizing death.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)