Are American cars better than foreign cars?

I need to know why do american cars most of the time only last til about 140,000 miles or so? Why do foreign cars go for 230k easy? I do realize that some American cars go for much longer then 140k, and some foreign cars don't go for long. But of the majority, American cars, do NOT last as long as foreign cars. Why? Is that bad engine parts used on American cars? Do foreign cars have different types of metal for the parts? Such as some of the Honda's have aluminum heads.
Help!

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