I heard a video where a German gent from the Muhle company pronounced it Mew-lah. Slight empasis on the first syllable. That's one that someone could have problems with since it's not really something an American would ever see and try to pronounce in the USA.
Hey, we're American (or at least I am), and speak American English. Close is close enough IMO. If I was trying to make sense to someone from Spain, then maybe the Spanish pronounciation of Vie-Long would be called for but for me just reading the words and making the American sounds works fine for me. Same goes for Semogue, and the others you mentioned. BTW, if I was trying to make sense to someone from Spain, they better speak English, 'cause I only know enough Spanish to get into trouble and not enough to make bail.
Maybe I'm an ugly American, but I just sound it out using American dialect. Now Muhle, that's different, try sounding that out...way too many possibilities if one doesn't know a little German.
One thing I've learned with the advent of the internet... the written word has no accent. Just spell it correctly and the person on the other side of the monitor understands perfectly and in his dialect. That has even been recognized by some software tech services too (Trend Micro specifically). We may not understand the gent from India if he speaks to us, but when he's connected to the computer, working on it remotely, and we're communicating by typing, his English is perfectly understandable as long as he can spell. By golly, when I read it he even writes in the dialect that I use!

Brian
Maker of Kramperts Finest Bay Rum and Frostbite
http://www.krampertsfinest.com/
Or find it here: Italian Barber, West Coast Shaving, Barclay Crocker, The Old Town Shaving Company at Stats, Maggard Razors; Leavitt & Peirce, Harvard Square