Can you post a photo? There is no way that small amount of trimming you said you did would "traumatize" any tree to the degree you describe. I'd suspect something else is not right and my first choice would be watering. Katsuras are thirsty trees and do not tolerate high heat and dryness well. I had a weeping katsura planted in my old garden that would routinely lose its leaves in summer if I was not out there watering deeply at least once a week! But it always revived and would leaf out as normal the next spring.

We need pictures to make any kind of useful suggestions. Trimming it wouldn’t kill it if was healthy, or even put it into shock. (Although annual trimming is not at all necessary.)

how about some pix

The small amount of snipping would not have caused the whole tree to shrivel - have you had a hotter and drier summer this year than before? Do these slow trickles for 2 hours spread out over the root area to make a broad puddle before soaking in? Or is there just a small wet spot off the end of the house after all that time? If the latter you are deeply watering a narrow column of soil and missing most of the tree's roots.

Saving Your Trees From Drought! – The Garden Professors™