For those who are not familiar with USA revolutionary history, the Boston Tea Party was a riot against an increase in tax on imported tea imposed by the king of England without any consultation with the British North American colonies. The actual complete phrase was "No taxation without representation." The irony is, many Trump supporters are not saying anything about Trump's unilateral decision to impose tariffs, bypassing the representation Congress is supposed to provide.
Alt text: A two panel comic. Top panel has a title of 1776, and a white man is yelling angrily. The word bubble says "Pay a 3% tax on tea and paper. Screw that! Revolution!" The bottom panel has the title Now and a white man looking despondent. The word bubble says "Pay 40% of your income. Sure that's totally fine."
The revolution was spurred on by the Stamp Act which required a tax on everything from tea to playing cards. Not only was it a lack of representation but the whole situation that the colonies were expected to be part of England but weren't treated like it. Now in the Crown's defense England was spending a lot on defending the colonies but they still should've given them a seat in parliament. If they had done that we might still be part of the UK or ended up like Canada (taking longer to leave).