IA is pronounced YA

The sound made by placing the two letters I and A together should be YA, as the German word for affirmative. I don't know why but many people here in the greater Philadelphia area, pronounce each letter separately and most of the time the letter I as an E.  The same with the word Pennsylvan E A.  What is the basis for this?  Is it the influence of romance language speaking immigrant population that swelled the area in the early 20th century?  I don't speak any languages other than American English and even that I don't use to its full potential.  I did study Russian at Central High School but that is mostly gone from my swiss cheese brain.  (Although, my minds races when I hear people speaking, what sounds like, the Russian language.  I search for phrases I remember, like на завтра or до свидания and to say something in Russian to them as they leave, hoping they will think I understood everything they just spoke.)  For all that I have forgotten, I do remember the Russian language has a letter in its alphabet that is я, pronounced YA.

My grandparents emigrated from eastern Europe and spoke forms of Slovic languages.  At my birth it was decided I would be named for both my grandfathers, Damian and Timofay.  However, my mother didn't know how to spell Damian.  She heard the name pronounced and the IA in the second syllable sounded like a YA,  when ending with the letter N she thought the second syllable should be spelled YON.  So before leaving the hospital she had to give me a name, for legal reasons, so she spelled it phonetically, D A M Y O N.  Now my mother also assigned me a nickname, Dan.  It has been much easier to tell people that my name is Dan than to constantly try to get them to pronounce my name as it should be.  That is problematic, too.  If I only tell people my name is Dan, they sometimes want to be proper and call me Daniel.  At this point, I have to decide whether to tell them that my name is not Daniel but Damyon and explain the whole story starting from my mother using phonetic spelling or just let it roll off my back and ignore it or say, "Call me anything but not late for dinner!"  You couldn't tell it by looking at me but, I have missed few dinners in my life.