First of all, the US dollar is not accepted anywhere at all in Paris, Italy, or Spain.   Don't even try to use it.  On my small group tours to Paris, Spain and Italy I give my travelers the following advice:

Use a credit/debit card wherever possible:   Make sure the credit card does not have a foreign transaction fee that adds on another 3% to a charge made on a credit/debit card.  Bank cards offer the most current and accurate exchange rates with no surcharges added in.   Make sure to advise your bank of travel plans before departure.

Money Exchange Kiosks:  Probably the worst place to exchange money.   The commissions are excessive at places like Travelex and American Express.  Don't do it.

Your Bank:  Probably the 2nd worst place to exchange money.   Fees and mark-ups can be excessive.   The only reason you might want to do it is to have some euros in hand upon arrival, and I don't even think that is necessary.

Bank/ATM cards:   Just about all ATM's will accept your bank card.   You'll get the fair exchange rate.   Although it is not necessary, I prefer to use a bank card that has some sort of affiliation with a large bank in the country you are visiting.   Also check with your bank to make sure there are no foreign transaction fees.

Dinner:  On my small group tours to Italy and Paris for instance, we all go out for a meal where we contribute individually.   If a few diners throw euros into the pot to pay for the meal, I will take that money and pay the bill with my credit card.   A fair exchange rate for everyone!