You've clearly not been paying any attention to what has happened to the judicial system in this country. Trump and Elon are both infamous for ripping people off and often getting away with it via the (compromised) court system.

https://www.reuters.com/legal/elon-musk-beats-500-million-se...

And even if they were to 1. find an uncompromised court, and 2. win a judgment to get paid... Who is ordered to pay them? The Treasury, which is under the control of...? You guessed it! The very people who do not intend to pay.

If they get judgement from US court can they enforce it in another country where US government has some assets?

In theory they could send baliffs to collect. Maybe they could try claiming assets located in a blue state?