Roughly 2/3s of the states in the US have “right to work” laws, which basically means that either employer or employee can terminate the job at any time for basically any reason.
That's not what he is talking about. You can also always quit your job in Germany.
He is talking about payments that are conditional upon you staying at the company for a certain amount of time. Relocation bonuses and stock option vesting are a very common type. If the bonus is high enough, it makes it very unattractive to quit. He is exaggerating though.
