Final answer:
The incorrect vocabulary word is 'assimilate' in the context of labor unions joining a federation; 'affiliated' or 'associated' would be more appropriate.
Step-by-step explanation:
The vocabulary word used incorrectly is assimilate in the sentence 'Many unions were assimilated with the American Federation of Labors.' The correct term should likely be affiliated or associated, as 'assimilate' typically means to absorb and integrate into a wider society or culture, which doesn't quite fit the context of labor unions joining a federation. The other vocabulary words: commerce, self-regulate, and reforms are all used correctly within their respective sentences.