Has Mezcal has been called a substitute for absinthe without the wormwood?

No, absinthe substitutes are generally Aniseed type drinks, with a flavor profile somewhat similar to absinthe.

Some historic brands in USA that dated from the Post-Prohibition era were Mohawk's Abson, Jung & Wulff's Milky Way, Dubouchett Alstina, Solari's Green Opal, and Legendre Herbsaint.

Legendre Herbsaint is the longest surviving Absinthe substitute made in the USA, which will celebrate it's seventy fifth anniversary in 2009.

More about the history of Legendre Herbsaint here: www.neworleansabsinthehistory.com