How to nest records in an Avro schema?

According to other sources on the web I would rewrite your second address definition:

mySchema = """
{
    "name": "person",
    "type": "record",
    "fields": [
        {"name": "firstname", "type": "string"},
        {"name": "lastname", "type": "string"},
        {
            "name": "address",
            "type": {
                        "type" : "record",
                        "name" : "AddressUSRecord",
                        "fields" : [
                            {"name": "streetaddress", "type": "string"},
                            {"name": "city", "type": "string"}
                        ]
                    }
        }
    ]
}"""

Every time we provide the type as named type, the field needs to be given as:

"name":"some_name",
"type": {
          "name":"CodeClassName",
           "type":"record/enum/array"
 } 

However, if the named type is union, then we do not need an extra type field and should be usable as:

"name":"some_name",
"type": [{
          "name":"CodeClassName1",
           "type":"record",
           "fields": ...
          },
          {
           "name":"CodeClassName2",
            "type":"record",
            "fields": ...
}]

Hope this clarifies further!