In my state they require:

>160 hours of education/vocational training and 2 years’ verifiable experience in the trade

To get the license to install minisplits (two years experience generally means working an apprenticeship).

It's no wonder install costs are so much in the US. And as you've experienced, they're hardly rocket science to install. The 160 hours training would be more than enough, I'm not sure why 2 years experience gets tacked on the end.