Assigning JSON object to variable from google sheets URL?

The data being returned is jsonp so you need to specify that in your Ajax request.

function getData() {
    return $.ajax({
        url: 'https://spreadsheets.google.com/feeds/cells/1r56MJc7DVUVSkQ-cYdonqdSGXh5x8nRum4dIGMN89j0/1/public/values/R29C4?alt=json-in-script&callback=importGSS',
        dataType: 'jsonp',
        jsonpCallback: 'importGSS'
    })
}

And while you can assign the data to, say, a global variable this will only get you so far - the Ajax process is asynchronous and you won't be able to access the data until the process has finished:

var obj;
getData().done(function (data) {
  obj = data;
});

// console.log(obj) here will return undefined as the process
// has not yet finished

Much better to grab the data and do something with it:

function doSomethingWithData(data) {
  console.log(data);
}

getData().done(function (data) {
  doSomethingWithData(data);
});

Or even simpler:

getData().done(doSomethingWithData);