Yes, we do. I say “we” because I was born and raised in northern California.
1) When people sing (well) they sound like West Coast Americans. This is regardless of how heavy their accent is in speaking. For an example would be the songs in the movie The Commitments.
I haven’t seen that movie, but with regard to singing, there are some vast differences between singing and speaking. Many of the vowel differences are lessened due to deliberately affected pronunciations (and sometimes really strained rhymes), elongated vowels, and the mechanics of singing. One of my friends was a vocal major and the drills he did for singing were incredible. If you’re trained operatically, you learn to manipulate every, and I mean every, part of your vocal apparatus. Those who are less trained will naturally fall into certain ways of producing the sounds because it produces less strain and is more understandable by most people.
2) An Australian friend talking with my mom said that he was softening his accent while in the US so he could be more easily understood. Further, he said that it was actual easier talking that way.
I can believe he was softening his accent to make himself understood more easily. If you went to Australia, depending on their amount of contact with American accents, you might have to affect a slight Australian accent to make yourself understood. I don’t know if it is easier talking with a west coast accent or not since that’s my native dialect. I do know that saying, “Dunno,” with an Australian drawl is a lot easier than saying, “I don’t know.” Doesn’t prove anything one way or the other though.
3) As a West Coaster, I couldn’t “soften” or “lay on” the accent. I can’t even begin to think how I could try to do so. While as I can perfectly well think of how to do so with any other accent I can do myself.
Of course you can’t “soften” it, you obviously don’t know what it is about the way you speak that makes your speech distinct. For the same reason, you can’t exaggerate it.
4) There is no “regional accents.” I couldn’t tell you if a person came from LA or Oregon, let alone which area of town he was born and raised in. The closest I have ever experienced was when I called the big interstate freeway “The Five” rather than “The I Five”, which is a dialect issue rather than one of accent.
And I would say that this probably means that you’re from southern California because unless northerners have been picking up more regionalisms since I’ve been out of the country than I’ve been aware of so far, someone from the Sacramento/Stockton area would say, “take 5” or “take I5.” Adding a “the” before a freeway/highway is a southern California thing. They also use words and phrases normally reserved for people when describing the roads: “The 5 was being a total bitch today. I couldn’t even get to my exit for, like, 20 minutes.”
A roommate when I was living in San Diego referred to Coke, 7-Up, Mountain Dew, etc. as “pop.” He lived about an hour south of Seattle. I can tell if someone is from Oregon or Washington within a minute or two, usually. There are some differences in speech patterns between the Bay Area and the Central Valley that are pretty subtle unless you’re from the area, but that do exist. I can almost certainly tell if someone’s from farther south than Fresno, and there are differences in the LA area between many of the different cities. Ask someone from West Covina if they can tell the difference between the way someone from from Burbank and Fontana sounds. I’ll bet there’s probably a difference, though I’m pretty sure I wouldn’t catch it as I’m not a native Angelino.
You probably just don’t listen to the differences very well, or don’t have the right aptitudes for picking up on them. Nothing wrong with that. Most musicians don’t have perfect pitch, but they can still play. You’re not a linguist, so you’re untrained in listening for the difference. Without a natural gift similar to perfect pitch, training to hear the difference, or a strong interest in dialects, you’ll probably miss most of the subtleties. That doesn’t mean they’re not there.
For the record, I pronounce “king” with a more lax vowel than I do “keen,” which is definitely a tense vowel. There is a distinct difference to me. The other minimal pairs hold up pretty well though.