Why Queen Elizabeth is not a light carrier

Should American ships be called fleet carriers while Britain's Queen Elizabeth class is treated as light carriers?

No. A roughly 70,000-ton Queen Elizabeth-class ship is a strike or fleet carrier; light carriers sit much farther down the size and capability spectrum.

Carrier classification depends on scale and role rather than nationality. The Queen Elizabeth class reaches roughly 70,000 tons at full load in the comparison given here. That makes the term light carrier misleading even beside larger American nuclear carriers. The British term strike carrier and the American term fleet carrier describe much closer categories than the proposed contrast suggests.