2. Enforcing compliance with basic laws hurts farmers. It's not clear to me that it's currently possible to operate an American farm both legally, and profitably. Laws that farmers are likely breaking have to do with employment, immigration, animal cruelty, and pollution. Compliance with all of this will drive your expenses up, and you out of business. This is a classic case of a prisoner's dillema - your competitors, who break the law, will undercut you, if you comply with it.
3. Larger farms with better access to capital are often better suited to take advantage of government subsidies.
4. Farming is incredibly risky. Your margins are razor-thin, and your yields and revenues are entirely at the mercy of the weather, and the capriciousness of your incredibly expensive equipment. Large, well-capitalized mega-farms are better suited to weather runs of bad luck, then smaller, family-ran ones.[1]
[1] Not to mention that many family farms rely on family members to operate. And if uncle Bill ruins his back on the job, in June, he's not going to be in shape to work at harvest time...
Governmental help comes in the form of lacklustre subsidies, or too small and too delayed financial aid, while at the same time providing massive grants to companies that are in the agri business system.
One example is the legislation of allocating "water rights" to the main river systems here, all of which has caused farms to go bankrupt, the middle men to get rich and we now have increased rice (!! Rice in Australia) production.
You'll notice that families who've been cobblers for generations can't compete with Nike on price, either. Economies of scale and international wage arbitrage really matter.