Yesterday I did it in a Real Life game.
My opponent didn’t expect that and after I said “America delcares war on ALL neutrals” and saw me moving 12 land troops from Gibraltar to Spain and 12 more land troops from transports in 101 to Spain, then landing all british aircrafts in Spain he said: OH SH1T!!
In fact, this saved me a LOT of time to intervene in Europe (It was btw after I contained Japan, with a moderate KJF strategy, a turtle UK in europe case he was treatening Sea Lion and turtle and retreat Russia)
The game ended arond turn 12 with him conceding with Japan reduced to 6 or 7 IPCs from Russian territories (Japan convoyed), Italy convoyed with US subs, and Germany close to Moscow but unable to take it.
I had Spain with waves and waves of troops from spain to normandy, southern france, france, north italy, a minor ic for building new ships if needed directly in sz91, or 3 tanks.