humorously i believe Greece and the US were the only countries contributing to NATO what all NATO members agreed needs to be contributed to NATO as of like 2012. Greece I assume was just overpaying their soldiers btw, seems about right for them
now, the us, france, britian, greece, turkey, and estonia are contributing at least 2% gdp (which is what the NATO members agreed on). poland is at 1.9, and rising. i think these contributions are in direct response to russian aggression, with little estonia for example, ramping up military expenditures.
the only time the coalition has fired from an attack was 9/11. it was such a strong coalition that it has helped maintain peace. the annexation of crimea is the first annexation in europe since wwii.
in the advent of an actual war, it is likely most european countries inside the nato alliance will jsut contribute as they have been, with some stepping up. but all of them will be under nato leadership, which is of course helmed by america. they'd all join, the prestige loss from not answering a call to arms is too great, but their level of contribution will never be that of america's. france and to a lesser extent england can project force if they want to though, and would be at the forefront of anything involving a european theater, same as it's ever been. germany actually has somewhat of an army these days, and if we let them, could be another military powerhouse, but it's a subject that no one wants to talk about.