Although most US farms are small farms, they are in decline and also far less productive, so the vast majority (85%) of output comes from large-scale farms.
Furthermore, because the agricultural system and all of the regulations support large-scale farming, small-scale family farms have to work within the system. (eg, http://www.businessweek.com/stories/2009-02-05/more-on-the-s...).
The trend is toward more factory farming, not less, since small scale farms are less profitable, often not covering costs. The difficulty of making small farms sustainable is generally attributed to the regulations, infrastructure, and economic realities increasingly favoring large scale factory farming.
If you doubt any of what I've said here, the USDA and others have plenty of reports available: http://www.ers.usda.gov/publications/err-economic-research-r...