Moving from England to America, how hard?

Say I met a man, and he wanted me to move to America. Never met him before. How easy is it to emigrate?

Firstly, I’m not independent, I would need him to look after me until I was confident alone.
How about his old life before me, could we just live and be accepted there?
What happens if it all goes wrong, for someone like me?

This isn’t happening, just something I was thinking of this afternoon.