Кто же такой "маршал" в американских фильмах? Почти всегда переводчики это слово не переводят, а так и говорят: маршал охотился за ним по всей Калифорнии. Но в русском языке маршал - высшее воинское звание, так что считать такой перевод правильным я не могу. Найти точный эквивалент в данном случае трудно, но можно, если знать основные варианты. В США "маршал" это обычно: федеральный инспектор (близок по функциям к шерифу), судебный исполнитель, пожарный инспектор. Так что для простоты можно всех американских маршалов переводить шерифами, если они ловят преступников, или инспекторами, если они занимаются чем-либо другим.

American Heritage Dictionary предлагает такие толкования:

a. A military officer of the highest rank in some countries.
b. A field marshal.
a. A U.S. federal officer of a judicial district who carries out court orders and discharges duties similar to those of a sheriff.
b. A city law enforcement officer in the United States who carries out court orders.
c. The head, especially of a fire department in the United States.
d. A fire marshal.
A person in charge of a parade or ceremony.
A high official in a royal court, especially one aiding the sovereign in military affairs.

1. To arrange or place (troops, for example) in line for a parade, maneuver, or review.
2. To arrange, place, or set in methodical order: marshal facts in preparation for an exam.
See Synonyms at  arrange.
3. To enlist and organize: trying to marshal public support.
4. To guide ceremoniously; conduct or usher.
1. To take up positions in or as if in a military formation.
2. To take form or order: facts marshaling as research progressed.
[Middle English, from Old French mareschal, of Germanic origin.]
Hard-riding marshals of the Wild West in pursuit of criminals reemphasize the relationship of the word marshal with horses.

The Germanic ancestor of our word marshal is a compound made up of ·marhaz, “horse” (related to the source of our word mare), and ·skalkaz, “servant,” meaning as a whole literally “horse servant,” hence “groom.” The Frankish descendant of this Germanic word, ·marahskalk, starting from these humble beginnings, came to designate a high royal official and also a high military commander, not surprisingly so, given the importance of the horse in medieval warfare.

The word passed into the period (beginning in 800) in which we speak of Old French, after the Franks and their Germanic language had been fused with the surrounding culture descended from Roman Gaul. When the Normans established a French-speaking official class in England, the Old French word came with them.

The Middle English source of our word is first recorded as a surname in 1218 (and the surname Marshal, now spelled Marshall, has been held by some famous people), but it is first recorded as a common noun with the sense “high officer of the royal court” in the first English language proclamation (1258) by an English king, Henry III, after the Norman Conquest.

Marshal was applied to this high royal official's deputies, who were officers of courts of law, and the word continued to designate various officials involved with courts of law and law enforcement, including the horseback-riding marshals we are familiar with in the United States.