Europeans used to dine just like Americans, eating with their fork in their right hand, until the 1840's.
Then, the British upper classes stopped shifting their forks back to their right hand and just kept their forks in their left hands to dine.
In 1853, a French etiquette book stated that if one wanted to appear fashionable and "In the Know", one should not shift one's fork back into the right hand while dining, thus began the European "Continental" style of eating. Before long, Europeans of all classes started eating in the Continental style.
In many European countries, eating in the American style is still suspect after seven Centuries. Folk Lore states that in the 14th Century, men eating together, (the women ate in the kitchen), used to hide daggers up their sleeves, then stab each other after the meal commenced. Stabbing at the dining table became so wide spread, the King finally put forth a decree stating everyone sitting at the table must have their wrists above the table, so all others may see no one is hiding any daggers up their sleeves.
An American Diplomatic Attache recently went to Germany on business. He ate in the American style with his right hand keeping his left hand in his lap throughout the entire business meal. The Germans at the table thought the American Attache was hiding something. They perceived him as dishonest. The German Host called the American Ambassador to Germany the next morning and told him: "Next time, send an Attache with a bit more style." This Attache thought he was "In the Know", but in fact, he "didn't know what he didn't know."
Both Continental and American styles of dining are correct. Be comfortable with the one you choose and stick to your choice! So, as history clearly states, it was the Europeans who changed styles, not the Americans!