Google returns that a dollar is now one Euro. What is a reasonable exchange rate? How do tourists in Paris acquire Euros at the best possible rate?
Same as always, get your money from an ATM, which is often the cheapest option, but it does depend on your bank and the contract you have.
Otherwise, exchange offices or bank offices which do money exchange, but in those cases do check as they often use a worse exchange rate. Sometimes post offices act as money exchange offices as well, not sure if that is the case in France.
The only time I get the exchange rate the sites show is when I exchange money with friends and we agree to use the exchange rate of a (named) site or service. In almost all other cases you pay a surcharge or cost.
When the UK pound and the Euro were at about the same level and the UK was still in the EU, the best you would get was 1.02 to 1.00, which was called one to one, as the rest was normal cost. From the US you will likely have higher costs.
It has been years since I have exchanged currency (in the country where that currency is used). I am from India and I use my Indian debit cards to withdraw local currency from the ATMs or directly at the stores wherever I visit.
I have two debit cards, both are visa cards. One card has 0% markup over the visa exchange rates and has unlimited international ATM withdrawals. The other has 2% markup over visa rate, also unlimited ATM withdrawals. I mainly use the first one, and keep the second one for emergencies. I also have a credit card, but it has 3% markup so I never use it, but also keep it for emergency usage.
You can get daily visa or mastercard rates at their websites.
Once you know those rates, you can see what markup a particular exchanger is charging and take your decision appropriately.
Best is to read the rates charged by your bank at its website. And shop around for cards which don't charge currency markup and directly use them abroad.
You can get some cash in your own country before you leave. Never exchange currency at airports as the rates offered are really bad.
For visa cards, you can use this link to see the exchange rate for any date:
As an example, just yesterday I withdrew 200 Euros from an ATM in Barcelona, using my Indian debit card (the one with 0% mark up). The amount debited from my account was INR 16018.27, which is exactly as per the rates mentioned on the visa website. If it was an American card (with 0% markup), 200.62 USD would have been deducted from my account, as per yesterday's visa exchange rates.
Using good credit or debit card at the ATM or at the shop will typically be more favorable than patronizing a money exchange office. What's the cheapest way of paying by card abroad? gives some details on how to optimize card use, but the summary of that you should look at minimizing the exchange rate, ATM fees and your bank's fees. Note that the visa exchange rate is less favorable than the market exchange rate (= it's a "hidden" fee).
What is a reasonable exchange rate?
The market exchange rate, as some banks offer. Anything less favorable means you're paying some fee to some bank.
It depends a lot on the banks involved and the currencies, but often, you get a better rate if you pay with a credit or debit card than if you convert to cash. However, that's for equal amounts: often you pay more commission on small amounts, so it may end up being more expensive to make many small purchases with a foreign card than to convert the equivalent amount to cash. However (again), unless you come back to the country often, if you get cash, you'll have some wasted cash left over at the end of the trip.
Since Covid, cards are accepted pretty much everywhere in Paris, without a minimum purchase amount.
If you do want cash, your options are to withdraw it from an ATM or to go to a bureau de change. Again, it depends, but generally withdrawing from an ATM is cheaper than changing cash at a random bureau de change, and even more so, than a bureau de change in an airport or tourist location. On the other hand, some bureaux de change in certain districts have very good rates. (But you pay for it with the hassle of 1. bringing cash from home and 2. having to travel to the place.)
I'm not going to recommend a specific store in Paris, and I don't know of an accurate comparison site. In Paris, there are stores with good rates in an area around Gare du Nord and Gare de l'Est. There's also a clutter of stores a bit further south-west near the stock exchange (Bourse) but I think they tend to be a bit more expensive.
Another option can be to convert the cash at home. Again, this tends to be a cheap option only if you live near a financial district, and definitely not if your only option is the airport.