Uhh, the callbacks aren't from node. The fallbacks are from vanilla JavaScript. You just notice them more in node, because you're doing event stuff, like making http connections. You have callbacks in browser JavaScript when you use AJAX.
It's a very strange comparison to me. JS is intrinsically tied to the DOM, HTML and Web technologies, the underlying VM has widely used open-source implementations (V8, WebKit, Gecko), and JavaScript is not controlled by any single company.
My comparison was of a more practical nature and practically speaking the most distributed VM is the browser.
The browser itself used to be too slow for many use cases which led to Flash filling in the gap, but thankfully that's rapidly changing with improved JIT VMs and HTML5 standardization efforts (WebRTC e.a.) all leading to the eventual demise of Flash.
Hence; JavaScript is the new ActionScript.
P.S. They're both just ECMAScript flavors so in that sense I would say they're very close ;)
Not even close.