Merida International Airport (MID). For those flying in from the US there are usually layovers at larger international airports (like MIA, DFW or IAH). We recommend selecting a flight that has a layover within the US vs. Mexico City if possible.
Yes, Merida is considered the safest city in all of Mexico and sits in the safest region in the country - the Yucatan!
If you are traveling from the US and are a citizen, you simply need to have a valid passport at the time of entry. No additional visa needed. Please note, US passport renewals are taking ~18 weeks to process, so please take this into consideration if your passport is expired or will expire before the wedding.
You don't need to have a car as there are plenty of Ubers across Merida. Your hotel can also call you a local taxi if needed. Transportation will be provided for events outside the city, so you don't need to worry about that. That said, there is a lot to do in the outskirts of Merida, so having a car would be recommended if you plan on doing more traveling before or after the wedding!