I did not know that Mexico could OUCH the US

Well, here is the evidence:

http://money.cnn.com/2017/02/13/news/economy/mexico-trump-us-corn/index.html

And since the deal is in favour of the US farm seller, such a bill if enacted is going to OUCH a significant body of the US electorate.

If this is what Mexico can do, think of what China could do?

The world is such a small inter-connected village. 

You can be the big boy on the block, but there can be serious repercussions if you stomp on others in the neighborhood. They can run a pole up your . . . !