I'm not quite sure how one would even measure the "foreignness" of a loanword. Perhaps have a text for people to read out loud and see how they pronounce some loanwords, or if they hesitate before the words or phrases. If people pronounce a word by naturalizing its "foreign" pronunciation into something more accommodating to English phonetics, that word has probably been "anglicized". Although some words never seem to lose their "foreignness", e.g., deja vu (even if it has lost its accents), schadenfreude (part of whose definition seems to include the German language or the German people).

Ceci n'est pas un seing.