The only Pre-European tobacco that grew east of the Missouri River was Nicotiana Rustica (a.k.a Yellow Henbane). N. Rustica has an average nicotine content of 9% compared to 1-3% of N. tabacum (most commonly smoked modern tobacco). This would have made it incredibly potent, possibly capable of causing altered states of mind and hallucinogenic effects.

Circa 1613 tobacco (n. tabacum) was introduced from the Caribbean to Virginia and production (and habitual use) of this strain increased.

So there is possibly little difference between modern tobacco and tobacco from the 1770s unless any changes in production method (not my area of knowledge) had any serious effects. However there was a big difference between pre-contact/European settlement tobacco and 'colonial' tobacco, at least in the Eastern Seaboard area of North America.

Sources: Barbour, P. L. (1986) The complete works of Captain John Smith, 1590-1631

McKenna, T. K (1993) Food of the gods: The search for the original tree of knowledge: a radical history of plants, drugs and human evolution.

Winter, J. C (2000) Tobacco Use by Native Americans: Sacred Smoke and Silent Killer.

EDIT: some formatting and clarity