Unions can be a highly controversial topic, as it touches upon some of people's basic political opinions. But at the risk of alienating readers I will delve into this topic.
With its single entity structure and its USSF sanctioned status as the only Division I league in America, MLS has a monopoly on top tier league soccer in the US. As is it is employers usually hold bargaining power over the majority of workers as they have more resources available, but when the employer has a monopoly the workers are few alternatives, and the ones they have have big consequences. In this case it would mean a lower level of soccer, or moving to another country, both of which would mean big changes in either the careers, the personal lives or both of the players.
This position has allowed MLS to keep costs down, which not only helped them in the early formative years, but also continues to be a source of pride (source) for the league. As many American and Canadian players have gone to college prior to their career and many seem to have studied business, they might have the a bigger appreciation and understanding of the necessity of this, but as employees with bargaining power that is comparatively smaller than their counterparts in other leagues as they have a harder time pitting the teams against each other for the players' benefit, they need another tool.
This tool is the players' union. It is the union that gave the players the leverage pressure MLS to raise the minimum wage for developmental players from $12.900 to $33.750 as soon the economics of the league allowed it. It is also exactly these players that the players' union should fight for. The top players have the value of their skills to get non-trade clauses, and other extra benefits, but for the young guys, they need the union the ensure that they have proper health care, some level of job security, and other somewhat quite rights. Ensuring these basic rights will also allow the players to focus more on their career and develop as players.
The fact that the MLSPU has focused on job security (guaranteed contracts) and the minimum salary, rather than more grander demands, show that they acknowledge that they are in a completely different situation than the NHL players' association, and that this is responsible representation of player interests, rather than class warfare.
One overlooked issue however, is the position of semi-pro players in the US and Canada. MLSPU only represents MLS players, and Eddie Pope confirmed to me via Twitter, that despite the fact that they can seek advice from MLSPU, there is no union for NASL, USL-Pro CSL players.
I think Eddie Pope and the rest of MLSPU should consider a change, where they go from being a league specific union, to representing the interests of all professional soccer players in the US and Canada. I am certain that the semi-pro players have an even more urgent need for representation to help them. Not so much to increase wages, but more so to ensure the basic things that allow them to improve their quality of life, but also to help them with career advice and career planning, that will help them make choices that are good, not just for their career, but also their lives.