Reigning RBS 6 Nations champions Ireland however began their tournament with a disappointing 25-22 loss to France in a thrilling finale while Scotland were comprehensively beaten by Australia 58-13.
Perhaps the most pressure was on England's shoulders as they took on the Pumas in front of a raucous crowd in Rosio.
Argentina came flying out the blocks scoring two converted tries through Ramiro Moyano and hooker Emiliana Coria which were both converted by Ignacio Rodriguez Muedra.
England kept in touch through the boot of Tom Homer who finished with an impressive 23-point haul but it was the intervention of outside centre May that turned the match.
His first try saw him cut through two tackles while his second owed to some brilliant work by winger Marcus Watson and his hat-trick try was touched down in the corner after the ball was spread wide.
Flying winger Christian Wade also crossed as did barn-storming captain Jacob Rowan to cap a resounding win for England who have lost in the final to New Zealand two years running.
Wales - who hosted the 2008 tournament - on the otherhand were outscored by Samoa two tries to one from Beck but relied on the boot of Matthew Jarvis for victory,
Fly-half Jarvis - on the books of the Ospreys - slotted six kicks out of seven to finish with a haul of 17 points while in contrast Samoa only landed one kick out of seven despite scoring first-half tries through Lole Tualaulelei and Joe Sililoto.
France's Gilles Bosch inflicted more pain on Ireland as his last-gasp kicked secure a vital win for Les Bleus.
Bosch kicked five penalties in their 20-15 defeat of champions Ireland in the Six Nations and his intervention was again decisive.
Moments after James McKinney had converted Simon Zebo's try to level the scores at 22-22, Bosch kicked the winning penalty.
McKinney kicked 17 points while France shared the points around with Antoine Erbani getting their only try and Jean Marc Doussain banging over four penalties.
Aussie winger Aidan Toua matched May's hat-trick with three tries of his own in Australia's romp over Scotland who did get a consolation try through winger Dougie Fife.
Fellow Tri-Nation teams South Africa and defending champions New Zealand recorded 40-14 and 44-11 victories over Tonga and Fiji respectively.