Do I need to worry because display capabilities (screen sizes, number of colors, etc.) of computers vary in other countries?
In the past (until the 90's) customers outside the United States and Europe often had less capable computer systems than those in the U.S. It was common for other countries to lag two to three years behind in getting the latest in personal computer technology. This gap has significantly decreased in recent years.
Similarly, in older text mode operating systems it was common for the number of lines of text on the screen to vary. For instance while most U.S. and European systems allowed 25 lines of text on the screen, some Japanese systems had fewer, because the display height of Japanese characters is greater (to allow better differentiation given the complexity of the characters) and some systems reserved one or two lines for a "Front End Processor" (the equivalent of today's Input Method Editor). Variations also existed between various vendors' hardware in Japan until a standard system emerged.
Today there is less need to make special allowances for hardware limitations in other countries for desktop displays - BUT many similar considerations SHOULD be kept in mind for the following reasons:
So, even though hardware variations across locales are not much of an issue now, the same sort of measures are often still needed, though for different reasons.