Suppose you found someone at your competitor who is doing your exact same job (already unlikely - their have a different structure in some way that is important) who is better than you. Would they be willing to move to where you company is? Would your company be willing to pay enough to make them join? Even if the above are true, all those structures your company has that are different mean there will be some time before they are better than you.
Most jobs don't need the best person. Is my doctor the best in the world - probably not - but she is more than good enough for my needs.
Though I have to object to your 95% number. Most people in the world do not have the education that the US provides. Most people are not fluent in English which is almost always a critical part of working for a company in the US. Once you add those requirements, the something closer to 50% of the most qualified people for your job live in the US (now if New Zealand was your country 95% of the most qualified don't live there - and most probably wouldn't want to move even though it is apparently a nice country)
Which is to say even if there was unlimited immigration allowed, your best hire in the US will be an American in most cases.
Though it doesn't matter who is most qualified you need to a plan to mentor and train up the younger generation. (who then grow old and train the next generation)