I recommend using the awesome requests library:

import requests

url = 'http://maps.googleapis.com/maps/api/directions/json'

params = dict(
    origin='Chicago,IL',
    destination='Los+Angeles,CA',
    waypoints='Joplin,MO|Oklahoma+City,OK',
    sensor='false'
)

resp = requests.get(url=url, params=params)
data = resp.json() # Check the JSON Response Content documentation below

JSON Response Content: https://requests.readthedocs.io/en/master/user/quickstart/#json-response-content

Since you're using requests, you should use the response's json method.

import requests

response = requests.get(...)
data = response.json()

It autodetects which decoder to use.

For reference, let's see what the original JSON would look like, with pretty formatting:

>>> print(json.dumps(my_json, indent=4))
{
    "name": "ns1:timeSeriesResponseType",
    "declaredType": "org.cuahsi.waterml.TimeSeriesResponseType",
    "scope": "javax.xml.bind.JAXBElement$GlobalScope",
    "value": {
        "queryInfo": {
            "creationTime": 1349724919000,
            "queryURL": "http://waterservices.usgs.gov/nwis/iv/",
            "criteria": {
                "locationParam": "[ALL:103232434]",
                "variableParam": "[00060, 00065]"
            },
            "note": [
                {
                    "value": "[ALL:103232434]",
                    "title": "filter:sites"
                },
                {
                    "value": "[mode=LATEST, modifiedSince=null]",
                    "title": "filter:timeRange"
                },
                {
                    "value": "sdas01",
                    "title": "server"
                }
            ]
        }
    },
    "nil": false,
    "globalScope": true,
    "typeSubstituted": false
}

That lets us see the structure of the data more clearly.

In the specific case, first we want to look at the corresponding value under the 'value' key in our parsed data. That is another dict; we can access the value of its 'queryInfo' key in the same way, and similarly the 'creationTime' from there.

To get the desired value, we simply put those accesses one after another:

my_json['value']['queryInfo']['creationTime'] # 1349724919000