britain survived for years against nazi germany despite being far less prepared for war in the 1930s than they are right now. because it turns out it's really hard to force an island nation with an excellent air force (and adequate if diminished navy) to capitulate when all your forces are pent up in europe. especially when britain has recourse to global trade that their enemies do not. also: britain has nukes, and its most important allies have nukes. why do russia's fanboys seem to think putin is the only one with nukes?
United States