UK. From 19 July, most restrictions will be lifted.

Update. From 19 July, most COVID-19 restrictions will be lifted. Border controls, quarantine, testing, and self-isolation for positive COVID-19 cases and close contacts remain.

From Monday 19 July you will not need to quarantine on arrival in England or take a day 8 COVID-19 test, as long as you:

• have been fully vaccinated under the UK vaccination programme.
• have not been in a red list country or France in the 10 days before you arrive in England.
• You must fill in a contact locator form before arriving in the UK. 
  
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• From Monday 19 July, UK residents who are fully vaccinated through the UK vaccine rollout, and children under 18, will no longer have to self-isolate when returning to England from amber list, including which is Spain, destinations apart from France.

Please visit https://www.gov.uk/uk-border-control for detailed public health advice and requirements for entering the UK

IRELAND. From Monday, July 19, 2021, Ireland will reopen its borders for non-essential travel.  Not only will foreign visitors, including Americans, be allowed to visit, but the Irish too will be able to travel without quarantine when returning home.
Unvaccinated travelers will need to show proof of a negative COVID-19 PCR test taken within 72 hours before arrival into the country and quarantine for five days. All people arriving in Ireland must fill out a Passenger Locator Form online at least 48 hours before arriving in Ireland.