Visa and Mastercard are accepted in the Republic of Ireland. Since Covid there has been a big push to contactless payments. Before Covid, the contactless machines would recognize an American card and print out a receipt for you to sign. If you don't have a chip and pin / contactless card, you will have issues at self service machines which don't have an option to print a receipt for you to sign.
Our hospitality, tourism and social industries are shut down right now and most likely wont be open before the summer, and when they reopen there will be big changes. When in person dining was allowed for a few weeks in 2020, people had to book online for a reservation and many places were asking for a deposit. There were also limits on the amount of people in a party, the amount of parties allowed in the restaurant and the amount of time parties were allowed to stay at a table. It is expected that due to the lockdown, that huge amounts of restaurants, bars and tourist places will not reopen. Many restaurants and bars have changed their layouts due to social distancing and have installed plexiglass partitions.