critical mass?

does anyone know where to get critical mass seeds-mr nice that will ship to the usa?

You could try Sensibleseeds.com.
Critical Mass | Mr-nice Seeds | Sensible Seeds

Here are some threads to help you decide:
https://www.rollitup.org/seed-strain-reviews/68457-sensibleseeds-com-review-ships-us.html
https://www.rollitup.org/seed-strain-reviews/85716-sensibleseeds-com-any-good.html

I may try them one day for Attitude doesn't carry Mr.Nice & Seed Boutique hasn't had Black Window in stock for months.

Good Luck!