Honda I know isn’t union, and it’s because Honda gives their workers similar treatment to union shops. Management got integrity or something. Every so often the unions go in and test the waters, the Honda workers say no need, we’re already treated well, and the union goes away.
Unions mostly exist as a response to shitty management. That and as a hiring hall, but that concept doesn’t apply to factory work. Construction contract work is where that is useful.
Volvo is a Chinese company now. The car side was sold to Ford a long time ago, leaving the original Volvo as a commercial truck manufacturer. And then Ford sold that car division to Geely. It’s long removed from the company that built its reputation.