Union recognition is then the company accepting that the union exists and then agreeing to meet and engage with it.
Not accepting it, is usually a crappy corporate move in an attempt to not have workers collaborating together.
Lots of research shows that generally places where unions exist have better work conditions and perform better over the long term.
The US has lower union involvement than in many countries.
Do you have any non-partisan sources for this? Genuinely curious. When you say perform better what do you mean specifically? And does better work conditions include better pay or just on-site conditions or something similar?
They earn more and are more productive. Here is one Canadian study but I’m sure you can find more if you’re interested.
It’s quite common that that also extends to negotiation on salary bands, and it’s also quite common the company then applies the same salary bands to non union employees also, rather than the norm in tech of individual negotiation. Many people think they’re in the group that is negotiating outlier salaries and would lose from this. However, many people with that viewpoint are also wrong about their position in the salary scale.
Sometimes this extends to promotion criteria and some unions push for tenure or seniority based promotions. This may or may not be better than your individual companies specific combination of merit, nepotism, the political clout of your managers and the business criticality of your department.
One thing that happens in the US that is illegal here is some companies agree to becoming a union shop and make joining the union compulsory.