FromAmerī̆ca +‎-ānus(“-an”).

• (Classical Latin)IPA^(key):/a.me.riːˈkaː.nus/,[ämɛriːˈkäːnʊs] orIPA^(key):/a.me.riˈkaː.nus/,[ämɛrɪˈkäːnʊs]
• (modern Italianate Ecclesiastical)IPA^(key):/a.me.riˈka.nus/,[ämeriˈkäːnus]

amerī̆canus (feminineamerī̆cana,neuteramerī̆canum);first/second-declension adjective

1. (New Latin)American; of or pertaining toAmerica (i.e. theAmericas)
   • 1723, Gervas Ludovicus Nicolaus de Oskierka,Theses ex universa philosophia quas ad majorem Dei gloriam & magnae Dei Matris Virginis Mariae honorem praeside R. P. Marquardo Rotenhan Societ. Jesu, Heidelberga (Heidelberg), sectionContinuatio globi terra quei in suas partes divisi,p.13:

     America in ſeptentrionalem, Auſtralem & InsulasAmericanas diſtribuitur.

     (pleaseadd an English translation of this quotation)

First/second-declension adjective.