The Free Masons. The organization I said earlier that Washington and several signers of the Declaration of Independence belonged to. It's a square and compass, important components to masonry/building.
It is indeed similar, but considering the Free Masons are the ones with the Order of the Knights Templar, I'm not sure how they would explain having a similar emblem to the assassins... Unless they intentionally created one similar to the assassins? For what purpose they would do that, I dunno.