JSFiddle - React, Tailwind, and code Playground

JavaScript

var data = [
{
    "State_Code": "01",
    "County_Code": "000",
    "State_Abbrv": "AL",
    "County_Name": "ALABAMA",
    "DATA": "12345"

},
{
    "State_Code": "01",
    "County_Code": "001",
    "State_Abbrv": "AL",
    "County_Name": "AUTAUGA COUNTY",
    "DATA": "123"

},
{
    "State_Code": "01",
    "County_Code": "003",
    "State_Abbrv": "AL",
    "County_Name": "BALDWIN COUNTY",
    "DATA": "321"

},
{
    "State_Code": "02",
    "County_Code": "000",
    "State_Abbrv": "AK",
    "County_Name": "ALASKA",
    "DATA": "98765"

},
{
    "State_Code": "02",
    "County_Code": "013",
    "State_Abbrv": "AK",
    "County_Name": "ALEUTIANS EAST BOROU",
    "DATA": "456"

}
];

var newData = { name : 'USA', children : [] };

for(var i=0; i<data.length; i++) {
	if(data[i].County_Code == "000") {
		newData.children.push({ name : data[i].County_Name, state_code : data[i].State_Code, children : [] });
	}
}

for(var i=0; i<data.length; i++)
{
	if(data[i].County_Code != "000") {
		for(var x=0; x<newData.children.length; x++) {
			if(data[i].State_Code == newData.children[x].state_code) {
				newData.children[x].children.push({ name : data[i].County_Name, data : data[i].DATA });
			}
		}
	}
}


console.log(newData);
document.write(JSON.stringify(newData));