However, whatever that need was (to hedge against the British) should have been completely necessary, and really goes to show you just how valuable a strong diplomatic corps can be to a country.
The British wanted to be pro-Union. They wanted slavery gone. They didn't want to have to station huge numbers of troops in Canada, or large numbers of ships in the Atlantic.
Silly, unforced errors by Seward & Charles Francis Adams (the American ambassador) antagonized Britain throughout the war & made them unsure of their North American holdings. Ridiculous. Union diplomats should have been talking peace & partnership with Britain from day 1 of the conflict.
tbf, we had moral reasons for wanting slavery gone but practical reasons for thinking we were better off with a divided America and an independent Confederacy as a useful source of cheap cotton. Some would say our political positions haven't got more realistic since. :)
I wonder how much the Union's need to hedge against British intervention—so, to divert resources away from the war against the South, affecting troop placement, artillery availability, fortification building/maintenance/garrisoning, and fleet positioning—prolonged the war.