RP to American Pronunciation

I'm 32 years old.
All of my English learning has been to imitate RP pronunciation.
Now that I'm in the US, they find it complicated sometimes to understand my accent.
I sound non-native with a little RP, a sound that their ears are not used to.
I have been thinking about switching to the American accent.
However, my r is non-rhotic and I can't do anything about it.
What would be your tips ? A voice coach?

All the best,

Josney