Firstly, I think it just really comes down to usage...

From the onset of immigration and as late as the 40s 50 & 60s, the majority of Italian-speaking Americans lived in ethnic neighborhoods where the language was being utilized. By the second generation, many Italians moved to mixed suburbs where there was no need to speak Italian.

Secondly, the Italian they did know was probably dialect which has an even broader limitation. It generally cannot be used amongst Italians from other regions and for the most part cannot be written with ease

A third dynamic (which often occurs but not always) is the amount of time passed since the point of the family's immigration. For example, the oldest child usually has a better command of the native language because his/her parents spoke limited English. By the time the fifth child or 10th grandchild is born, the native speakers are mostly fluent in English as well as all the other siblings born before... therefore the language picked up is English rather than Italian

These are my thoughts, theories.... etc...

There is some merit to your thoughts as well Mauro. When my parents arrived in this country in the late 50's early 60's, the couldn't speak English so it was only natural that the first language we were taught was Italian (dialect to be exact). As a matter of fact, I vaguely remember it being somewhat of an issue when we started school because they were concerned about how much English we really knew. As we grew up, my parents learned the language. In fact they both tried hard to speak, read and write English (first Dad because he was out in the workforce and then Mom because she put it in her head she wanted her drivers license-) and we helped them learn. WE were first generation Canadians.

So that brings us to today. My husband is of Italian/Czech descendant but his mother came to this country as a child and he only speaks English..my brother married an English woman and my sister married an Italian man. My children do not speak Italian as it was not the language my husband and I communicate in. My brother and his ex did not speak Italian either so their kids don't speak it as well. My sister's children understand Italian but don't speak it and I think this is because my mother lived with them for ten years and spoke to them in Italian.

The war thing doesnt count for me..I was born after the war.

My mother was born here. Out of 9 kids, only the oldest 3 spoke italian. My fahter was born in italy, but came here at age 9. They spoke english in the home. However, my husbands father was born there, the mother here..they spoke a lot of italian in the home, yet only one spoke italian, the oldest and he learned it in school.

My mother and her sister spoke italian when they didnt want us to know what they were saying. I think I began to know more than what she thought..lol

My grandparents were both Italian born but come to this country as children at the turn of the century. My dad said that they always spoke to each other in English, unless they didn't want the kids to understand. My dad also said that my grandmother would speak to her own mother in English, even though her mom only spoke Italian back. He said that it had to do with assimilation and that they embraced being Americans by not speaking the language of the old country. My grandmother even changed her name to an American one and disregarded the Italian naming traditions with her kids. My dad took Italian in school and did not learn from his parents although he leaerned dialect expressions from his parents.