In the sentence 「米国内には75の孔子学院があり、うち65が 米 大学内に 設置されている。」
「うち」seems to be used to convey the same message as「のうち」but without requiring the の particle which is present in all the Bunpro example sentences for 「のうち」as well as having a different format, in this case 「NのAがあり、うちN2」
With N being the ‘out of’ number and N2 being the portion of N in question.
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Hey 
It is exactly as you say, basically meaning “among these” and so on. You can think of it as このうち with この omitted.
I hope it helps,
Cheers!
PS
I think we can add example of this!
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