I have no doubt in my mind that most programmers would at least listen to the pitch if it was to join a guild.

And yet guilds are traditionally vehicles for monopoly and control. All the things Americans complain about with regards to unions, are actually guild-like behaviour.

Yes, but guilds are also the names of player-formed free associations in MMOs, which are what jumps to most software engineers' minds when they hear the word.

And in labour organisations "guild" has some unfortunate racist conations in the USA.

Serious question - maybe the word "union" or "guild" is a branding problem? We could do some basic user research and come up with a more appealing name.(Think Universal Basic Income -> Freedom Dividend)

I'd be more likely to join an organization called "Gathered Friends for Salary Negation And Fair Treatment".

A lot of early US workers organisations where called guilds and one of the aims was excluding BAME (to use a modern term) workers.

Also Guild does imply exclusion which is the medieval guild system which I think others have mentioned.

What racist connotations?

The good old game of term switcheroo, Americans like to play it a lot