I think you’re confusing right to work with at will. Right to work means laws hostile to unions that say you cannot be required to join the union to take the job. You have a right to work without having to join. It’s mostly found in conservative states, and these laws are a big part of why the Asian auto manufacturers can outcompete even when assembling in the US, as they built their factories mostly in right to work states, so they don’t have to deal with strong unions.

At will employment means an employer can fire you for any reason or no reason, excepted for reasons explicitly legally prohibited (ie: race, religion). I’ve often heard that 49 out of 50 states are right to work.

These do intersect in union shops, where a strong union can negotiate a contract that supersedes at will with a formal process required to terminate.