The chances of someone being a foreign agent increases significantly if they are from a foreign country. Meaning if you have foreign friends there is a small but non-zero chance that they desire, for their home country, the sensitive information you are being trusted to protect.

You are not going to lose or be rejected for a clearance because you have a few foreign friends. It is just another one of those things you have to report to the government (meaning the government issuing the clearance).