The term Belgian Standards (often abbreviated as BS) originally referred to the relatively lower standards of attractiveness to which American expatriates held their compatriots while living abroad. The Belgian Standard has been colloquially dubbed "the expat's beer goggles" in reference to poor sexual decisions expatriates frequently make under its influence.
Another common reference to Belgian Standards is the Belgian Ultimatum, similar to the Desert Island Ultimatum in which one person asks another if they would sleep with a member of the opposite sex when stranded on a desert island with no other options. However, in the Belgian Ultimatum, the proposed scenario is generally used as a more subtle technique to suss out whom an individual would sleep with if they had to lower their standards substantially, but still retained a nominal modicum of selectivity.
An often-confused similar term, British Standards, denotes the opposite phenomenon, in which Americans living abroad begin to hold their American peers to higher standards based on the relatively higher attractiveness of the native inhabitants of the foreign country in which they live. In such cases, the so-called All-American moral values of the opposite sex simply do not cut it and fail to substantially improve the attractiveness of fellow expatriates.
"He might be autistic and from Iowa, but against Belgian Standards he's looking pretty good."