This is from the Multilingual PC Directory:
An accent mark placed above a character. Used in languages such as Czech, Latvian, Lithuanian, Croatian, Slovak, Slovene, Wendic and many transliterated languages. (Also called a Hácek mark). (cf. accents).
Beside of these transliteration systems that you mention from America, there are the German system (Jelzin, Tschaikowsky), the Serbocroat(?) system (Jelcin, C<hácek>ernomirdin), and there used to be (since the 70s) a common Scandinavian system that wasn’t always followed.
A hacek or hácek (“?”, pronounced HUH-check), also known as a caron, is a diacritic placed over certain letters to indicate palatalization or jotation in the orthography of some Slavic and Baltic languages.
A *HACEK* or hácek (pronounced “ˈhatchek”), a.k.a. *CARON* is a diacritic placed over certain letters to indicate palatalization in the orthography of some Slavonic languages, such as Czech, and the Baltic languages.