When some or most of your target acquisition is outsourced

Recently, an investor told he had invested in a search but not a searcher's acquisition target because the company he wanted to buy had too many employees outside of the US. In his words, 80% of the company could be gone tomorrow (the searcher would be located in the US.) There were a handful of employees in the US, the corporation was based in the US but they utilized a large outsourced engineering team.

Here is my question, when exactly does it make investors nervous that there are too many employees outside of the HQ country? In SaaS and many other industries, it's very typical to outsource engineering or manufacturing elements. I am curious if this was just one investor or if there are many others that have this concern. Is there a tipping point when outsourcing makes investors feel uncomfortable? Feel free to share any stories.