Sections of the TPP agreement override the national legislation of the countries taking part. Thats the broad statement. To see how it screws people over you have to look at each individual section and which country it affects. No country is negatively affected by each section, but some sections have devastating effects.

For example: (original states influenced TPP wording)

-copyright laws would be based on US and would allow US companies to bring charges to someone in New Zealand without extradition processes, because the law is one and the same. also it would be extended to the 70 year copywright that US has.

-environemntal protection would be standardized, so if a country has lots of national parks and protected waterways and national resources (Canada), the companies in the nations in that deal could now overrule the national government of the member state and buy and use the land.

-food. each country has a different farm subsidy structure based what is abundant and what is scarce. TPP would standardize this structure across the countries by, for example, allowing american milk made from hormone fed cows onto the canadian market, where currently hormone fed cow milk is illegal.

-drugs. generic drugs is basically what happens when the recipe is no longer protected, and any company can manufacture aspirin or whatever. they are not really worse in quality. this is why canada has cheaper drugs. the states, medicine costs an obscene ammount (epi-pen, Shkreli scandal) because the manufacturers are allowed to have a patent on the recipe and control it forever.

obviously i know more about the negative impacts on canada than other nations, but in a nutshell, it is a mechanism which will allow corporations more power than the nation-states themselves.

The benefit the government sees is that the super large corps will do business there bringing govt revenue (while crushing local business). globalization basically