Is there a way to Connect a raspberry pi to a aws react app?

Hi - Not very sure on your overall requirements on what is getting changed on the PI but one option is to use it as an IOT device which listens to a mqtt topic. The app which is react in this case can publish to the same IOT topic and then pi which is subscribed to that topic can read the payload and do the required changes. You can also you use device shadow which can make a device’s state available to apps and other services whether the device is connected to AWS IoT or not.

References

1. https://docs.aws.amazon.com/iot/latest/developerguide/topics.html
2. https://docs.aws.amazon.com/iot/latest/developerguide/iot-device-shadows.html

You can also check https://aws.amazon.com/iot-device-management/ which can help to register, organize, monitor, and remotely manage connected devices at scale