Here's a list of all the collections I've visited along with the years I visited and, for the US, the states:
United States
CT- Action Wildlife (2016)
NJ- Adventure Aquarium (2014)
NY- Bronx Zoo (Pre-2011, 2011, 2013, 2014, 2015, 2016, 2017)
FL- Central Florida Zoo & Botanical Gardens (2016)
NY- Central Park Zoo (2012, 2014, 2015)
OH- Cincinnati Zoo & Botanical Garden (2013)
CT- Connecticut's Beardsley Zoo (Pre-2011, 2012, 2014, 2015)
FL- Disney's Animal Kingdom (Pre-2011)
FL- Gatorland (Pre-2011)
CA- Los Angeles Zoo & Botanical Gardens (2016)
CT- Maritime Aquarium at Norwalk (2011, 2014, 2016)
CT-Mystic Aquarium & Institute for Exploration (2011, 2016)
NY- New York Aquarium (2013, 2016)
KY- Newport Aquarium (2013)
PA- Philadelphia Zoo (2014)
FL- Ponce Inlet Marine Science Center (2014)
NY- Prospect Park Zoo (2013, 2016)
NY- Queens Zoo (2016)
RI- Roger Williams Park Zoo (2012, 2015, 2016)
NY- Rosamond Gifford Zoo at Burnet Park (2017)
FL- SeaWorld Discovery Cove (2013)
FL- SeaWorld Orlando (Pre-2011)
D.C.- Smithsonian National Zoological Park (Pre-2011, 2012)
FL- St. Augustine Alligator Farm Zoological Park (2014)
FL- Tampa's Lowry Park Zoo (2013)
NY- Trevor Zoo (2016)
NY- Utica Zoo (2017)
PA- ZooAmerica: North American Wildlife Park (2012)
United Kingdom
England- Birmingham Wildlife Conservation Park (2016)
England- Bristol Zoo (2016)
England- Chester Zoo (2016)
England- Colchester Zoo (2016)
England- Cotswold Falconry Center (2016)
England- Cotswold Wildlife Park (2016)
England- Crocodiles of the World (2016)
Scotland- Edinburgh Zoo (2016)
England- Exmoor Zoological Park (2016)
England- Gentleshaw Wildlife Center (2016)
England- Hamerton Zoo (2016)
England- Hemsley Conservation Center (2016)
Scotland- Highland Wildlife Park (2016)
England- Howletts Wild Animal Park (2016)
England- Linton Zoo (2016)
England- Living Coasts (2016)
England- Newquay Blue Reef Aquarium (2016)
England- Newquay Zoo (2016)
England- Noah's Ark Zoo Farm (2016)
England- Paignton Zoo (2016)
England- Paradise Park (2016)
England- Port Lympne Wild Animal Park (2016)
England- Reaseheath College Zoo (2016)
England- Rodbaston Animal Zone (2016)
Scotland- Scottish Owl Center (2016)
England- Shaldon Wildlife Trust (2016)
England- Tropiquaria Zoo (2016)
England- Twycross Zoo (2016)
England- Wildwood Discovery Park (2016)
England- Wingham Wildlife Park (2016)
England- WWT Slimbridge Wetland Center (2016)
England- ZSL London Zoo (2016)
England- ZSL Whipsnade Zoo (2016)
*2011 was the year I started officially keeping track of the species I've seen and started visiting zoos more seriously. Before that my zoo visits were years apart and I don't remember much about the collections I've yet to visit since nor what I saw at them.
Number of Collections Visited in the US: 28
Number of Collections Visited in the UK: 33
The very first zoo I visited was the Smithsonian National Zoological Park when I was just a baby as we lived in a nearby D.C. neighborhood at the time.
~Thylo