Where there ever sightings or legends of Sasquatch or Sasquatch-like creatures during the American Revolution?

If by "sasquatch or sasquatch-like creatures" you mean reports of large, hairy, ape-like hominids, then certainly not; the earliest reports that have been co-opted into the sasquatch mythos date to the early 19th century, the term "sasquatch" did not come into use until the 1920s (when it was coined by a Canadian newspaperman named JW Burns), and "Bigfoot" not until the late 1950s.

That is not to say that there weren't reports of "things in the forest" that antedate 1800. Before that time, however, they were not considered to be animals. There was, instead, a longstanding tradition relating to the "wild man of the woods," an essentially literary trope consisting of stories of hermits and outcasts. Such stories can be traced back a long way. Gerald of Wales, writing in the 1190s, describes Merlin in this manner; he had gone mad during a battle and "fled into the forest where he passed the remainder of his life as a wild man of the woods." This did not mean that the "wild man" was not human, nor that he necessarily had no contact with human society; Merlin was still able to acquire a reputation as a powerful magician and prophet. But it's possible to suggest that the "wild man" trope fills a roughly similar space in folklore to sasquatch. Neil Thomas, in his "The Celtic wild man tradition and Geoffrey of Monmouth's Vita Merlini (Arthuriana 10, 2000), argues that "it is evident that the figure of the Wild Man has arisen spontaneously in a number of cultures of a far greater antiquity than that of the Celtic lands of the post-Roman period," and he points to parallels dating as far back as the Epic of Gilgamesh.

A major problem in regard to early sasquatch/bigfoot reports is the uncritical appropriation by cryptozoologists of any and all fragments of legend or tradition that could plausibly (and often only implausibly) be regarded as distorted reports of "real animals". A good example which relates to your query is the "windigo" or "wendigo" of Canadian First Nation folklore. The windigo features in a highly-complex set of myths and cautionary tales, often appearing as an insatiable supernatural creature associated with dearth and cannibalism (I wrote a little about an early windigo cannibalism story, dating to 1741 and originating in the archives of the Hudson's Bay Company, here.) Because he is assumed to have once been human, and lurks in the deep woods, many of these tales feature traits that could be and have been stripped of their original contexts and co-opted in this way.

Chad Arment's The Historical Bigfoot (2006), a comprehensive but not critical compilation of reports, is a good place to start if you are interested in early North American sasquatch-style reports. The earliest cases he has gathered all feature "wild men" or "yahoos" (a term meaning, essentially, uncouth subhuman, popularised by Gulliver's Travels), progressing to "gorillas" later in the 19th century. There is an extensive literature on the windigo which places this group of stories in a series of more useful contexts than the cryptozoological one; see for example Robert A. Brightman's "The windigo in the material world," Ethnohistory 35 (1988) and DH Turner's "Windigo mythology and the analysis of Cree social structure," Anthropologica NS19 (1977).

Incidentally, when Burns coined the term "sasquatch," he did so by taking a word from the Coast Salish language group of British Columbia, normally given as "sésquac," which means "wild man."