Are there any treadmills that are American made?

There are a few - check Google. I found this:
https://www.lifefitness.com/commercial/cardio/treadmills/activate-series/activate-series-treadmill.html

Of course, the electronic components could still be made in Asia on "American built" treadmills.

If you're looking for quality, American-made doesn't necessarily mean top quality, as Harley-Davidson motorcycles have shown us.

Commercial-grade treadmills (from any country) tend to be higher quality, since they're intended for high usage in gyms. But they tend to be very expensive.