Can you wrap an external API to convert the authentication method from OAUTH to IAM?

Our project strongly revolves around interacting with multiple external APIs which are protected using OAUTH2. The problem we are facing is that we interact with these APIs through many AWS services all of which require different setups to authenticate with this api.

For example STEP FUNCTIONS requires an EVENT BRIDGE CONNECTION to authenticate with external APIs whereas for LAMBDA we had to spin out own solution which would store the active auth token in a secret and refresh it every hour. All of this results in massive overhead, complexity and latency to simply communicate with an external api.

Now my question is if it would be possible to wrap the external APIs in a service like API GATEWAY which would handle the OAuth flow with the endpoint and itself use IAM. This way all of our internal services can simply make requests to this API Gateway using IAM and then the wrapper forwards the request with the OAuth token.

I played around with one solution, which is to have an API GATEWAY which forwards request to a STEP FUNCTION which then makes the external API request and returns the response. This worked for most things but I hit a headend because one of the endpoints is for file uploads, and STEP FUNCTIONS can't handle binary data.