We have a small River Birch (around 7' tall) that was growing vigorously.
Lately we have noticed some of the leaves are a lighter green than the
others. Additionally, these leaves have a "wrinkled" appearance. When we
water the tree, lots of what appear to be wasps fly off of it. Is there a
wasp that attacks the leaves on this tree or do we have another as yet
unseen pest? What would the group recomend to control this outbreak?

It sounds more like you have a honeydew producing insect, most likely aphids.
Wasps do not feed on trees but do enjoy the honeydew.
sed5555