I don't know if the terms of the Trans-Pacific Partnership trade agreement will or will not benefit most Americans, although I suspect that they will be much better for the banks and the multinationals than for you and me. The reason I'm limited to suspicion is that the terms of the agreement, most of which already have been decided, are secret. I don't get to see them. Unless you are a US Senator or one of the corporate leaders and lobbyists who designed the deal, you don't know either. We commoners are not allowed in on the secret, and when our Senators get to have a peek, they're not allowed to take notes.
What I do understand, just by the nature of such agreements, is that the TPP is likely to have provisions that facilitate violations of our local, state, and federal laws — that is, the ability of business interests to sue governments to overturn laws that the corporations just don't like. Among those laws might be regulations bearing on health, safety, environmental protection, labor rights, banking, and more. To me, that sounds like a real danger.
More dangerous than the agreement itself is granting the President six years of fast-track authority to enter into trade deals — that is, the authority to agree to a deal with only 51 votes for approval in the Senate. If the next president (or, perhaps, the current president) decides to negotiate a treaty that castrates Dodd-Frank, for example, 51 votes would do the trick — not the 60 required to overcome a filibuster.
All the talk about loss of jobs is of little importance — but it's easier for ordinary Americans to understand than the far more virulent threats to regulation of banking, oil exploration and production, food and drug markets, and more. Fast-track makes the current plutocratic domination of American politics exponentially worse.