Any state where citizenship is civic. Canada is the exact same. On the polar opposite is a country like Japan. You can't become Japanese. You can become American.
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You can "become" Japanese since there is a procedure in Japan for it, but you can't "become" Japanese for being a citizen there. It's a bit complicated, but if I could sum it up in a nutshell, the actual Japanese won't treat you the same. They might look down at you, because of family traditions and such.