> A lot of US funds have restrictions as to how much they can invest outside the US.

I'm not sure that's relevant. ARM is listing American Depository Shares, so this is still usually viewed as an international investment.

Are you sure - I always thought the whole point of ADRs was to make foreign company shares available on the American markets?

In fact the SEC says

'ADRs allow U.S. investors to invest in non-U.S.companies '

https://www.sec.gov/investor/alerts/adr-bulletin.pdf

Why?

Not protected by US regulation and law.

So if you are a US pension fund that has all it's funds in Nigeria ( to pick an example ) - can it be said to be safe under US law?

Ironically the inverse problem EU countries have with US tech firms holding their citizens data - however it that case the response is generally 'la la la'.