Is working experiences outside of US meaningful?

I'm an undergrad student in S.Korea and major in economics(financial econ. & quantitative econ.)
I'm looking forward to walking in hedge funds or prop trading companies in the US as a quantitative researcher or strategist.
That's why I'll apply MFE program or Ph.D. in OR.
In this case, before going to the grad program, working as an intern or junior position at quant investment or trading in local firms is meaningful?
In terms of getting into a grad school(MFE, OR) or finding a job.

For now, I got the following experiences:
Research Consultant at WorldQuant
Research intern at the government-related institution(Korea Center for International Finance)
Summer intern in Quant invest division at the largest AM company in Korea(Samsung Asset Management)
Researcher under a professor in my school with another AM company about global macro asset allocation

Which is the better choice whether taking more courses in mathematics(analysis, PDE) or computer sciences?
all those will reflect well when you interview with US companies during/after getting an MS degree or something here in the States

Thank you for answering my question.
Anyway, you mean that these experiences are not meaningful by itself and the key point is knowledge which I get by experiences. Right?