.com - Which countries use .com?

I am from the UK.

Would like to promote my website in other countries... will using a .com be OK? or should I register domains using the correct extensions for each country. For example if I am targeting France use .fr

Basically I am trying to find out if .com is used world-wide or just mainly for usa and uk companies.

Will having .com look professional in other countries.

Thanks for your help.