Uranium mining has significant health risks, and it is pretty much guaranteed to result in significant pollution of the surrounding area. The enrichment phase isn't much better either.
Turns out the US has things like worker protection laws and environmental protection laws. Producing it locally is expensive, it is much cheaper to outsource the problem to a country with a more relaxed view on the issue.
A bit of googling shows there are about 1,000 abandoned uranium mining/prospecting sites in New Mexico. Probably many with uncontained tailings. Yikes. But we can count on extraction projects to clean up after themselves now. Right?