So, this really depends on where in the US you are going to speak Spanish. It's going to vary based on the community's make up. A place with higher Porto Rican people is going to have a different Spanish than a Guatemalan community or a Peruvian one.

So try and do a Latin American Spanish focused class and be prepared to be wrong when you actually talk with folks.

AI is improving in this regard. With the right set up, you're having conversations with a grammatically native speaker who isn't a real person, but who will talk as long as you want and gently correct and teach you without judgment as you go. May be worth checking out.

Good for you OP! Spanish is such a rich, beautiful sounding language.

My best bet, aside from full immersion is to first, take lessons in order to learn good foundations and know how stuff works and then, hire a language coach who can help you with your specific request.

Source: I help people doing exactly that. Some want to learn an accent, some want to lose an accent, some people need help getting more confident in their second or third language, etc.

The Babbel app Latin American Spanish course gets pretty close. There isn't some standard US Spanish but when I switched it from European Spanish to the Latin American one it got much more familiar. I am sure that would help and it is conversational language learning.

Check your local community colleges, you might be able to audit Spanish classes for a small fee. IIRC this means you won’t do tests, but learning from someone who actually speaks the language you’re interested in is a huge advantage.

Duolingo is okay, IME many other language learning apps don’t distinguish between Latin American Spanish and Spain Spanish. But as others said, there’s a LOT of regional variation even within Latin America. So even if you’re able to comprehend and speak it well you may still run into a lot of “wtf do you mean” when trying to talk to people, lol. Like learning British English and trying to understand wtf a Texan is saying: not impossible, just with a very different usage of vocab.