If I purchase a phone from the U.S. to use in Taiwan, would it work

If I purchase a phone from the U.S. to use in Taiwan, would it work?
I use the "IF card" (aka: pay-as-you-go card, but from Taiwan) and not through a network company, would this still work or do different countries have different size/shape SIM card (this is also the "IF card" here).
Cell Phones & Plans - 1 Answers
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I'm going to guess that your from the U.S. The sim cards are different here but the average Cell Phone shop can easily set you up with a reliable phone and easy Pay-As-You-Go plan.