Is Quilted available outside the US currently?

Yes, Quilted is available outside the US. International numbers may have issues, so it will be better to send those invitees via email. 
setTimeout(function() { var tidioScript = document.createElement("script"); tidioScript.src = "//code.tidio.co/PUBLIC_KEY.js"; document.body.appendChild(tidioScript); }, 15 * 1000);