for those who don't speak english as their first language, what strategies did you use to build confidence when speaking?

just accept the fact, that failure is part of the learning process. we've all been there. everyone is awkward sometimes. no one is perfect. “Success is not final, failure is not fatal: it is the courage to continue that counts.” or here's an other one. "Fear is a reaction, courage is a decision" — Winston S. Churchill

you don't really overcome that unless you stop give a f about everything, you get better at speaking, alone, through shadowing, mimicking, reading out loud. That is, if you had enough input to correct yourself or at least to know that something is off. Another thing we usually overlook is tongue position and stuff to pronounce sound we don't have in our language, often a result of reading much more than listening.

For what it’s worth, I have not seen much judgement as a native speaking adult in the US. Frustration sometimes, and maybe a little lighthearted joking for a certain kind of humor. But broadly speaking we understand that English is tricky to learn and we are generally used to a variety of accents, so the bar to fitting in is a lot lower than you probably think.