Nations sometimes do launch invasions that have no military chance of success.
Just look at the Argentine invasion of the Falklands in the 1980s.
Hmh? It was the British retaking of the islands that had virtually no chance of success. Thatcher decided to attempt anyway; had she faced that invasion just twelve months later, Britain would certainly have lost the islands, as the Royal Navy would no longer have had amphibious warfare vessels capable of operating across two oceans.
Any growth would have by necessity been away from the Romulans/Klingons. The growth would have been "asymmetrical."
Quite so. And even though ENT featured contact with Klingons, it didn't actually suggest border conflicts yet; the Romulans would be the closer enemy of these two.
Although one might also speculate that when Archer's heroes dispersed the Delphic Expanse, this rearranged national borders overnight, and saw both of Earth's expansionist neighbor empires engage in a conquest and expansion spree that brought them closer to Earth than ever before.