The USA saved England in WW 1 and WW 2.
Pretty moot - the Germans weren't going to invade the UK in either war by the time the Yanks got involved.
In WW1 the German objectives were limited to the continent - their Navy was never going to get control of the Channel.
In WW2 the risk of invasion passed once Hitler took on USSR in '41 - and certainly post-Stalingrad and Kursk there was only going to be one winner of that fight.
More accurately the USA saved the French twice - once from the Germans and then once from the Russians - and we all see how they have repaid you - might be another chance to google 'French Military Victories' though - which is always good for a laugh
That said the 'soft' assistance from USA in food and machinery was very helpful to the Brits during the dark times when we stood alone -on the other hand you did charge for it and it's taken us until now to finally pay off the last of that financial debt. The 2nd WW effectively crippled the UK as a financial power - it took us 40 years to stage much of a recovery..