qwerty - You're wrong on the need for Visa's for Argentines visiting the Uk, Ireland or any other European state, an Argentine does not require a Visa, either prior to arrival, or upon arrival. As in any country, you have to show signs of being able to support yourself upon arrival, and not give indications that you might be there for an alternate reason, like working. You are then stamped into the country, which I guess is what you are calling a Visa....
And us Europeans, do not need a Visa for the US for tourism, we travel on the Visa Waiver Scheme - I-94. And again we are stamped upon entry and granted 90 days tourist status, but in the US it is specifically called the Visa Waiver, but I understand what you mean....
Just for the record, the UK authorities are starting to clamp down on people coming into the country, thanks to the change in politcal colour of the government, so things may get tougher for Latin Americans there too...