Btw, many Law grads don't go into Law.
The degree itself is good for a very wide range of future careers - related stuff like government/Public Sector, journalism, think tanks, human rights, international relations etc etc, but also more general 'graduate roles' in the same way that degrees in History, English, Social Sciences are. And in this case, you need as many extra facets to your CV as possible. Employers value overseas experience (it is not regarded as a twee gap-year as one poster appears to assume) - and there are a many areas of work where personal experience of the US, combined with a 'sensible' degree like Law, would be a big plus. If its LLB its a qualifying Law degree - the world will always need lawyers and people who think like lawyers.
And Sussex is a good Uni. You'll hear a great deal of utter wibble on TSR about 'better Unis' and its mostly 'I've heard' rubbish.
Its always offered lots of joint subjects in the belief that a rounded education is better than a very narrow subject focus. You'l find Sussex grads in all sorts of surprising roles outside their degree subject as a result.. Its a smaller Uni - more friendly, less 'anonymous' and has lots of mature students and other folk who don't fit the 'normal student' mould - and its in a fabulously arty seaside town thats a 50 minute train journey to London. If this is what you want, go for it.