What architecture decisions you should consider while planning for international software’s?

Avoid hard coding of strings in the project. Any display right from labels to error messages read it from a resource file.
>Length of the string is also of prime importance. Itfs a noted fact that when we translate English language in to other language the words increase by minimum 30 to 40 %. For instance you can see from the below figure how the Hindi text has increased as compared to English text.

So all your labels, message boxes have to be designed in such a way that this text size mismatch is adjusted. Do not crowd all your fields on one screen you will definitely end with the text length issue. Leave some room for expansion.

Decimal separator varies from locale to locale. For instance 25, 12.80 in the United States is 25.12,80 in Greece or Germany. Yes you guessed right the decimal separator in Europe is a "," (Comma).
Calendar changes from country to country. Definitely Gregorian calendar is the most used. But there are some other calendars like Hebrew, Islamic, Chinese etc. All these calendars have huge differences. For instance Nepal follows Nepali Calendar which is 56.7 years ahead of Gregorian calendar. So according to cultural settings user can expect the dates accordingly.
Sort order is affected by language. You can see from the figure below Hindi and English languages have different sorting order.

Time varies from locale to locale. For instance an 8 PM in India is 20:00 in Europe. In Europe there is not concept of AM and PM.
If you are using built-in fonts use the resource file to bundle the same. You can load the fonts from the resource file rather than telling the user explicitly to install the fonts in his PC.
Keyboards layout changes according locale and region. So be careful while designing the short cut keys. The function keys are mostly present in all key boards. Probably you can consider the function keys for short cut keys. Below is a sample Hindi key board. If you define CTRL + V as a short cut for paste functionality it can create confusion for Hindi users on the below key board.

So you can see from the above points that making software adapt to global culture is not only related to string translation. It’s much beyond that.