I have loved Paris sionce I was ten years old and now I live only 2 hours away! But Parisians do have a reputation even among the French of being a bit snobbish and iffy towards visitors, even provincial French. However, they do appreciate being at least greeted in French, and being told how beautiful their city is (and it is!). And I have always found them helpful if approached in the right spirit. I have seen too many self-righteous visitors shouting in English and then being bewildered when they got a bad response. As said, you will get short shrift if you try to defend US foreign policy, but the French are quite capable of distinguishing between the Government and the visitor.
Coffees are expensive in Paris, even for us who live in France. But 3 course meals are often cheap and sometimes include wine. It is always better to go for the menu du jour (meal of the day) and most waiters will love to explain it to you, as long as you don't make a face if they suggest an option based on tripe ( there are always choices). Shopping goes without saying, and the area round the Opera has the best shops - though you should wander along the Faubourg St Honore to see the high fashion couturier salons and showrooms too.
Paris is a city for walking in. You cannot appreciate it any other way, so take good comfortable shoes and be prepared to hit tarmac. Avoid taxis. Take the metro to the area you want to explore, and a good guide book and large scale map, on which every street is shown. Musts are the Isle de la Cite, in the middle of the river Seine, with Notre Dame on it (and a fascinating bird market on Sundays), the Eiffel Tower (but going up it is expensive and can be a disappointment if the weather is not perfect - and NEVER eat in the restaurant at the top, it is a rip-off). Also Montmartre district with the Sacre-Coeur church (a better view of the city from there than the Tour Eiffel)and the artists' Bohemian quarter where you can get your sketch or caricature done and see the cafes where Toulouse Lautrec drew and painted the lowlife of his time. I love the Marais (French for marsh, which is what it used to be, being on low ground near the river) - it was the old Jewish quarter and still has good delis, and is now the gay centre of Paris and is very lively, with loads of good cheap restaurants and craft/art shops, especially round the Place des Vosges.
The Luxembourg gardens are lovely, with a good and not too expensive open-air restaurant, the CAtacombs and Pere Lachaise Cemetery are a bit creepy but utterly fascinating and you can see the graves of Oscar Wilde and many other famous persons, not all of them French by any means.
The Centre Pompidou is a modern Arts Centre, with the area round it (Chatelet) full of cafes, restaurants and street theatre on summer evenings.
And cross as many bridges as you can, on foot. Walk along the Seine, looking at all the book stalls, artists and fishermen, and the little boats going by. A trip by boat is moderately expensive, but can be fun on a nice day. My favourite museum is the Musee D'Orsee, in a converted Art Nouveau railway station, and contains impressionist and modern paintings, art nouveau furniture and ceramics, Greek and Roman statuary, and other things. And the building is amazing.
A good day trip is to Monet's garden at Giverny, easy to arrange and well worth while.
I love Paris, though you might not be able to tell!!