This is the 410th most frequent Czech word.
amerického
"Amerického" means "American" in the genitive or accusative singular masculine form, or genitive singular neuter form, in Czech.
The word 'amerického' here serves as an adjective in the genitive singular form modifying the noun 'umění' (art) to specify it as American art.
Navštívil jsem muzeum amerického umění.
I visited the museum of American art.
The word 'amerického' acts as an adjective in the genitive singular form modifying 'autora' (author) to indicate the author is from America.
Knihu amerického autora jsem našel na stole.
I found the book of the American author on the table.
The word 'amerického' here is an adjective in the genitive singular form describing 'vojáka' (soldier), indicating the soldier's American nationality.