Are Open Jam Sessions a Thing in USA Cities?

I’m an American, I’ve been living abroad for three years. In that time I’ve discovered a love of playing music, and I’ve gotten decent at it. In the city I live in, people get together at different bars multiple times per week to jam for a few hours. It’s awesome.

I never played music in the USA before I left, so I never looked for this before. Do people do that in America? Are there any cities where people do it a lot? Are they welcoming to new musicians?