How to promote in US?

Hello!

I'm an indie developer making a web application for Dev and QA teams - Qase.io. It is a test case management tool. A week ago, I've launched open beta test.

To promote it, I've asked an owner of the popular Russian telegram channel (~6k followers) to check my app and write a review. I've received hundreds of registration in one day. That was awesome. Facebook, google adwords, quora can't even compete with promotion in the professional community.

But for now, I have a problem. According to my research, US test case management tools market is the biggest (35%+ of market share) in the world. And I have no idea, how to find such professional communities in the USA.

Where should I start from?