Several other nations maintain aircraft carriers, and some of them are quite large.
The French and British can run air operations from a carrier, especially the French at this point. Both have at least one carrier of 70,000 tons. So it isn’t just the US that could field them.
The Italians and the Spanish both have active small carriers.
The Japanese have (I think) 3 to 5 “Helicopter Destroyers” which could in a matter of weeks be converted to launch and recover up to 35 STVOL aircraft each.
India has a carrier as big as the Chinese and is building two more. In fact, India has included carriers in their fleet for decades.
Brazil has a big old French carrier (Foch) but I do not know if it is operational.
Thailand has a small carrier but no planes and uses it as a royal yacht.
The Philippines have been making a bit of noise about buying a retired light carrier from Spain.
The French have one (troublesome) carrier, which displaces 42,500 tons. The UK's single carrier (another on the way) displaces 65,000 tons, but it's not fully operational yet.
The Japanese have (I think) 3 to 5 “Helicopter Destroyers” which could in a matter of weeks be converted to launch and recover up to 35 STVOL aircraft each.
4 of them. 18 maximum aircraft for the Hyūga-clasa, 28 for the larger Izumo-class....but Japan has only received a single F-35 so far, if I'm not mistaken.