The Proposal is the quintessential romantic comedy: two people having every reason to avoid each other are thrust together by improbable circumstances, despite their best efforts are compelled to learn wondrous facts about each other, and just as circumstances conspire to separate them one makes a heroic act to save and secure their love just as the other is leaving forever.
The situation is contrived, the embarrassing jokes compulsory, the plot predictable, the big reveal compelling, the supporting cast goofy, and it's all worth seeing again in a "have you seen..." pinch.
Oh, particulars? A boss-from-he11 executive needs an excuse to prolong an expired visa, so she (!) obligates the long-suffering loyal assistant to play fiancé. You can guess the rest.