Two more concerts have received additional dates for the first leg of the upcoming tour. Both take place the night after the first announced concert. The two new dates are:
 

• 8 May 2018 in San Jose at SAP Center
• 16 May 2018 in Inglewood (billed as Los Angeles) at The Forum
   

Regarding presales, U2.com states the following:

"Verified U2.com Subscribers who did not use their unique ticketing presale code to buy tickets in November's presales will be able to enter the presales for these additional shows starting next Tuesday , December 5th (10am) and running until Thursday Dec 7th (5pm). Qualifying subscribers will be emailed ahead of these presales. Tickets for these shows go on general sale on Monday December 11th at 10am.

Registration/Setup for Subscribers (new or existing) who have not yet registered and would like to take part in these presales is now open and will close this Sunday, December 3 (10pm ET / 7pm PT)."