Switching the US to be open shop would change my mind. This would allow people to easily switch away from or negotiate with abusive unions.
The unions I have dealt with have universally been more abusive than my employers, to the point where employers would try to sneak unauthorized employee benefits through contract loopholes. In one case the union agrees to let the company hire non-union labor (with capped, low pay and benefits) to do the jobs of union employees with seniority that refused to work and could not be fired.
If you think my repeated personal experiences with multiple national unions are all anecdotal outliers, then explain why wildcat strikes have become common in the US in recent years.