Hi Jen, thanks for the question.

Black spots on maple trees are not uncommon and for the most part, if not repeatedly subject to the same disease, are insignificant.  When conditions are right, these diseases tend to show up.  Check out the following links:

Maple leaf blister and anthracnose: Two diseases of maple leaves - Landscaping (msu.edu)

Maple anthracnose - MSU Extension

Black dots on maple: Tar spot - MSU Extension

Insect damage mostly comes from caterpillars.  Red maples are pretty resilient.  Young trees can lose up 30% of their leaves and mature trees up to 50% without significant harm unless it happens repeatedly.  Defoliation is less harmful from late summer on. 

I hope this is helpful.