Could the United States have converted a third battlecruiser?

Could the United States have secured enough treaty tonnage to convert Constellation as a third carrier?

Possibly, but only with a large carrier-tonnage increase and an equivalent British right to a third conversion.

Converting Constellation alongside Lexington and Saratoga would require a much larger treaty carrier allowance, roughly in the 160,000-ton range. Britain would probably demand the same right to convert three large hulls. The surviving Admiral-class hulls might then become carriers in place of Courageous and Glorious. The question therefore changes more than one American ship: it reopens the carrier tonnage bargain for every major treaty navy.