The verb tread in the sense of stepping or walking has been in the language for a thousand years. Its first citation in the OED (Oxford English Dictionary) is from the Beowulf manuscript (c. 975 AD).
American speakers still use tread and its irregular past tense forms trod and trodden, but not as frequently as British speakers do. For example, a British girl might say, “He’s a terrible dancer! He trod on my feet all evening.” An American girl would say, “He stepped on my feet.”
For American speakers, the verb tread in the sense of step or walk tends to have old-fashioned or historical connotations, as in the following title and headline:
The steps already trod : a history of First United Methodist Church, Salisbury, North Carolina
Where Camels Once Trod, a Train Crosses Australia
When using tread in the sense of stepping or walking, the standard past tense forms are trod and trodden.
The OED (Oxford English Dictionary) gives trod as the simple past tense and either trodden or trod as the past participle. It mentions the archaic past form trode.
Webster Unabridged also gives trod as the first entry for simple past and trodden or trod as the first entry for the past participle:
A common use of tread in US English—as both noun and verb—is in the context of restoring rubber to a tire.
Tread noun: The tread of a tire or track refers to the rubber on its circumference that makes contact with the road or the ground. As tires are used, the tread is worn off, limiting its effectiveness in providing traction. A worn tire can often be retreaded.
In the context of retreading tires, the past tense is formed with –ed:
Between 1910 and 1920, several ways were invented to retread a tire. In the beginning, tires were retreaded and repaired as needed. Radial truck tires were expensive, but they could be retreaded several times.
American speakers also tend to use treaded instead of trod in the context of swimming:
A Florida fisherman treaded water for 20 hours before being picked up
The first exposure to tread as a verb for American children probably comes in elementary school, when their history teachers show them a picture of the Gasden flag.
The Gasden flag (1775) used the image of a rattlesnake to represent the American colonies. The motto, “Don’t Tread On Me,” played on two meanings of tread. One is the literal meaning of “step on.” The other is the figurative meaning of “oppress” or “abuse.” Using a rattlesnake to represent the colonists suggested that doing otherwise would result in deadly consequences.
A modern version of the Gasden flag uses “tread” as a past participle instead of standard trodden or trod.