Sorry, forgot to give an explanation.
I thought of what they are trying to achieve with the MLS and how they want it to be one of the best leagues in the world even though it is relatively new and most of the teams currently aren't what anyone might call 'world beaters'. This made me think of the part of the concept of yin and yang where the whole is greater than the assembled parts.
I have tried to make the logo reflect the yin and yang symbol and include the relevant MLS aspects.