Dude there is no reason to switch your account, because PS3 and PS4 support having multiple accounts and both consoles are region free. You can share Digital Games, Physical Games, DLC on all accounts as well as the PS+ online multiplayer. Your current console in the US has to be the primary console on each account.
Basicley you can keep your UK account as the main account and make a second US account where you will download all your games and DLC from now one. Just make sure that the DLC is puchased from the region the game is originated. You cant for example download US DLC for a UK game, doesnt matter if its digital or physical.
The only problem is you have to decide where you want to have your PS+ from now on, if you stick with your UK PS+ you can keep your old PS+ library but it could end up being more expensive as you would pay in UK pounds in your new home.
US PS+ would be a lot cheaper but you couldnt use features like the cloud save feature on your UK account.
Multiplayer will work on any account if the console has an account with a PS+ subsciption.
You can buy PSN voucher codes from various websites, no credit card needed







