Less overwhelming than a lot of these things. In April there were 30000 troops from the European NATO countries in Afghanistan (link). At that time we only had 38000 troops there. There are also troops from non-NATO countries. Now we have close to 68000 troops in Afghanistan. Unfortunately I don't have time right now to look up all the latest figures for each country.
No it is an American war over 9/11 since America was attacked NATO was obligated to help out. NATO never would have had the guts to take on afghanistan if the US didn’t invade and rout them first.