Foreign accent syndrome is an extremely rare condition in which people suddenly can only speak with a foreign accent.
It usually happens after some kind of head trauma or stroke but in some cases, you could simply wake up and no longer have the accent you grew up with.
There can be a lack of understanding and compassion when this happens from friends and family. People tend to think it’s a joke or that they can simply force the accent to return. Life can be very challenging for the person with the newly acquired accent. Your accent is a part of your identity, losing it projects a different identity.