According to the toLocaleString() MDN Documentation the option hour: "2-digit"
should return a 2 digit representation of the hour, but it returns only 1 digit if the locale is en-US and the format is AM/PM. (Update: AM/PM mention)
let d = new Date("2019-05-03 15:00:00").toLocaleString("en-US", {hour: "2-digit", minute: "2-digit"});
console.log(d);
Is there a workaround or another easy way to get the 2-digit hour for the US locale, displaying the AM and PM?