If you want to work _on_ space then anecdotally I don't believe it's true that you have to be American citizen to work at NASA/JPL (you need a work visa etc.).

If you want to work _on_ space then anecdotally I don't believe it's true that you have to be American citizen to work at NASA/JPL (you need a work visa etc.). However ESA and others are doing plenty of cool things also!