Oh, I thought we were talking about anglophones pronouncing non-english words, not the other way around.

Japanese gets a pass on its loanwords because the language doesn't have the letters to pronounce a lot of words from other languages. It does the best it can. I don't know many English speakers who pronounce Llewellyn the Welsh way...

But if you're ordering a hamburger in Japan, there's probably already something wrong with you anyway. Unless it's at Gasto. In that case, enjoy your ハンバーグ.